mirror of https://github.com/python/cpython
585 lines
15 KiB
Python
585 lines
15 KiB
Python
# module 'string' -- A collection of string operations
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# Warning: most of the code you see here isn't normally used nowadays.
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# At the end of this file most functions are replaced by built-in
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# functions imported from built-in module "strop".
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"""Common string manipulations.
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Public module variables:
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whitespace -- a string containing all characters considered whitespace
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lowercase -- a string containing all characters considered lowercase letters
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uppercase -- a string containing all characters considered uppercase letters
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letters -- a string containing all characters considered letters
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digits -- a string containing all characters considered decimal digits
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hexdigits -- a string containing all characters considered hexadecimal digits
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octdigits -- a string containing all characters considered octal digits
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"""
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# Some strings for ctype-style character classification
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whitespace = ' \t\n\r\v\f'
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lowercase = 'abcdefghijklmnopqrstuvwxyz'
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uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
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letters = lowercase + uppercase
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digits = '0123456789'
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hexdigits = digits + 'abcdef' + 'ABCDEF'
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octdigits = '01234567'
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# Case conversion helpers
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_idmap = ''
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for i in range(256): _idmap = _idmap + chr(i)
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_lower = _idmap[:ord('A')] + lowercase + _idmap[ord('Z')+1:]
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_upper = _idmap[:ord('a')] + uppercase + _idmap[ord('z')+1:]
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_swapcase = _upper[:ord('A')] + lowercase + _upper[ord('Z')+1:]
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del i
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# Backward compatible names for exceptions
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index_error = ValueError
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atoi_error = ValueError
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atof_error = ValueError
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atol_error = ValueError
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# convert UPPER CASE letters to lower case
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def lower(s):
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"""lower(s) -> string
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Return a copy of the string s converted to lowercase.
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"""
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res = ''
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for c in s:
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res = res + _lower[ord(c)]
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return res
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# Convert lower case letters to UPPER CASE
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def upper(s):
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"""upper(s) -> string
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Return a copy of the string s converted to uppercase.
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"""
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res = ''
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for c in s:
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res = res + _upper[ord(c)]
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return res
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# Swap lower case letters and UPPER CASE
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def swapcase(s):
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"""swapcase(s) -> string
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Return a copy of the string s with upper case characters
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converted to lowercase and vice versa.
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"""
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res = ''
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for c in s:
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res = res + _swapcase[ord(c)]
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return res
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# Strip leading and trailing tabs and spaces
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def strip(s):
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"""strip(s) -> string
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Return a copy of the string s with leading and trailing
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whitespace removed.
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"""
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i, j = 0, len(s)
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while i < j and s[i] in whitespace: i = i+1
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while i < j and s[j-1] in whitespace: j = j-1
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return s[i:j]
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# Strip leading tabs and spaces
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def lstrip(s):
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"""lstrip(s) -> string
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Return a copy of the string s with leading whitespace removed.
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"""
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i, j = 0, len(s)
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while i < j and s[i] in whitespace: i = i+1
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return s[i:j]
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# Strip trailing tabs and spaces
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def rstrip(s):
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"""rstrip(s) -> string
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Return a copy of the string s with trailing whitespace
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removed.
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"""
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i, j = 0, len(s)
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while i < j and s[j-1] in whitespace: j = j-1
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return s[i:j]
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# Split a string into a list of space/tab-separated words
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# NB: split(s) is NOT the same as splitfields(s, ' ')!
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def split(s, sep=None, maxsplit=0):
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"""split(str [,sep [,maxsplit]]) -> list of strings
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Return a list of the words in the string s, using sep as the
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delimiter string. If maxsplit is nonzero, splits into at most
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maxsplit words If sep is not specified, any whitespace string
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is a separator. Maxsplit defaults to 0.
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(split and splitfields are synonymous)
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"""
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if sep is not None: return splitfields(s, sep, maxsplit)
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res = []
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i, n = 0, len(s)
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if maxsplit <= 0: maxsplit = n
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count = 0
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while i < n:
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while i < n and s[i] in whitespace: i = i+1
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if i == n: break
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if count >= maxsplit:
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res.append(s[i:])
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break
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j = i
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while j < n and s[j] not in whitespace: j = j+1
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count = count + 1
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res.append(s[i:j])
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i = j
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return res
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# Split a list into fields separated by a given string
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# NB: splitfields(s, ' ') is NOT the same as split(s)!
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# splitfields(s, '') returns [s] (in analogy with split() in nawk)
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def splitfields(s, sep=None, maxsplit=0):
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"""splitfields(str [,sep [,maxsplit]]) -> list of strings
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Return a list of the words in the string s, using sep as the
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delimiter string. If maxsplit is nonzero, splits into at most
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maxsplit words If sep is not specified, any whitespace string
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is a separator. Maxsplit defaults to 0.
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(split and splitfields are synonymous)
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"""
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if sep is None: return split(s, None, maxsplit)
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res = []
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nsep = len(sep)
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if nsep == 0:
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return [s]
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ns = len(s)
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if maxsplit <= 0: maxsplit = ns
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i = j = 0
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count = 0
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while j+nsep <= ns:
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if s[j:j+nsep] == sep:
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count = count + 1
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res.append(s[i:j])
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i = j = j + nsep
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if count >= maxsplit: break
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else:
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j = j + 1
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res.append(s[i:])
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return res
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# Join words with spaces between them
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def join(words, sep = ' '):
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"""join(list [,sep]) -> string
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Return a string composed of the words in list, with
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intervening occurences of sep. Sep defaults to a single
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space.
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(joinfields and join are synonymous)
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"""
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return joinfields(words, sep)
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# Join fields with optional separator
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def joinfields(words, sep = ' '):
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"""joinfields(list [,sep]) -> string
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Return a string composed of the words in list, with
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intervening occurences of sep. The default separator is a
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single space.
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(joinfields and join are synonymous)
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"""
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res = ''
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for w in words:
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res = res + (sep + w)
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return res[len(sep):]
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# Find substring, raise exception if not found
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def index(s, sub, i = 0, last=None):
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"""index(s, sub [,start [,end]]) -> int
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Return the lowest index in s where substring sub is found,
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such that sub is contained within s[start,end]. Optional
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arguments start and end are interpreted as in slice notation.
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Raise ValueError if not found.
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"""
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if last is None: last = len(s)
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res = find(s, sub, i, last)
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if res < 0:
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raise ValueError, 'substring not found in string.index'
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return res
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# Find last substring, raise exception if not found
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def rindex(s, sub, i = 0, last=None):
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"""rindex(s, sub [,start [,end]]) -> int
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Return the highest index in s where substring sub is found,
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such that sub is contained within s[start,end]. Optional
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arguments start and end are interpreted as in slice notation.
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Raise ValueError if not found.
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"""
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if last is None: last = len(s)
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res = rfind(s, sub, i, last)
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if res < 0:
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raise ValueError, 'substring not found in string.index'
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return res
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# Count non-overlapping occurrences of substring
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def count(s, sub, i = 0, last=None):
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"""count(s, sub[, start[,end]]) -> int
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Return the number of occurrences of substring sub in string
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s[start:end]. Optional arguments start and end are
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interpreted as in slice notation.
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"""
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Slen = len(s) # cache this value, for speed
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if last is None:
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last = Slen
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elif last < 0:
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last = max(0, last + Slen)
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elif last > Slen:
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last = Slen
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if i < 0: i = max(0, i + Slen)
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n = len(sub)
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m = last + 1 - n
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if n == 0: return m-i
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r = 0
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while i < m:
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if sub == s[i:i+n]:
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r = r+1
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i = i+n
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else:
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i = i+1
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return r
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# Find substring, return -1 if not found
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def find(s, sub, i = 0, last=None):
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"""find(s, sub [,start [,end]]) -> in
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Return the lowest index in s where substring sub is found,
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such that sub is contained within s[start,end]. Optional
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arguments start and end are interpreted as in slice notation.
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Return -1 on failure.
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"""
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Slen = len(s) # cache this value, for speed
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if last is None:
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last = Slen
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elif last < 0:
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last = max(0, last + Slen)
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elif last > Slen:
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last = Slen
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if i < 0: i = max(0, i + Slen)
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n = len(sub)
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m = last + 1 - n
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while i < m:
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if sub == s[i:i+n]: return i
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i = i+1
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return -1
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# Find last substring, return -1 if not found
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def rfind(s, sub, i = 0, last=None):
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"""rfind(s, sub [,start [,end]]) -> int
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Return the highest index in s where substring sub is found,
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such that sub is contained within s[start,end]. Optional
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arguments start and end are interpreted as in slice notation.
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Return -1 on failure.
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"""
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Slen = len(s) # cache this value, for speed
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if last is None:
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last = Slen
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elif last < 0:
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last = max(0, last + Slen)
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elif last > Slen:
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last = Slen
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if i < 0: i = max(0, i + Slen)
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n = len(sub)
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m = last + 1 - n
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r = -1
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while i < m:
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if sub == s[i:i+n]: r = i
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i = i+1
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return r
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# "Safe" environment for eval()
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safe_env = {"__builtins__": {}}
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# Convert string to float
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re = None
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def atof(str):
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"""atof(s) -> float
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Return the floating point number represented by the string s.
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"""
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global re
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if re is None:
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# Don't fail if re doesn't exist -- just skip the syntax check
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try:
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import re
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except ImportError:
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re = 0
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sign = ''
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s = strip(str)
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if s and s[0] in '+-':
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sign = s[0]
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s = s[1:]
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if not s:
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raise ValueError, 'non-float argument to string.atof'
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while s[0] == '0' and len(s) > 1 and s[1] in digits: s = s[1:]
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if re and not re.match('[0-9]*(\.[0-9]*)?([eE][-+]?[0-9]+)?$', s):
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raise ValueError, 'non-float argument to string.atof'
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try:
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return float(eval(sign + s, safe_env))
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except SyntaxError:
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raise ValueError, 'non-float argument to string.atof'
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# Convert string to integer
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def atoi(str, base=10):
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"""atoi(s [,base]) -> int
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Return the integer represented by the string s in the given
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base, which defaults to 10. The string s must consist of one
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or more digits, possibly preceded by a sign. If base is 0, it
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is chosen from the leading characters of s, 0 for octal, 0x or
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0X for hexadecimal. If base is 16, a preceding 0x or 0X is
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accepted.
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"""
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if base != 10:
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# We only get here if strop doesn't define atoi()
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raise ValueError, "this string.atoi doesn't support base != 10"
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sign = ''
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s = str
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if s and s[0] in '+-':
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sign = s[0]
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s = s[1:]
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if not s:
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raise ValueError, 'non-integer argument to string.atoi'
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while s[0] == '0' and len(s) > 1: s = s[1:]
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for c in s:
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if c not in digits:
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raise ValueError, 'non-integer argument to string.atoi'
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return eval(sign + s, safe_env)
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# Convert string to long integer
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def atol(str, base=10):
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"""atol(s [,base]) -> long
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Return the long integer represented by the string s in the
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given base, which defaults to 10. The string s must consist
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of one or more digits, possibly preceded by a sign. If base
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is 0, it is chosen from the leading characters of s, 0 for
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octal, 0x or 0X for hexadecimal. If base is 16, a preceding
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0x or 0X is accepted. A trailing L or l is not accepted,
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unless base is 0.
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"""
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if base != 10:
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# We only get here if strop doesn't define atol()
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raise ValueError, "this string.atol doesn't support base != 10"
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sign = ''
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s = str
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if s and s[0] in '+-':
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sign = s[0]
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s = s[1:]
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if not s:
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raise ValueError, 'non-integer argument to string.atol'
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while s[0] == '0' and len(s) > 1: s = s[1:]
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for c in s:
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if c not in digits:
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raise ValueError, 'non-integer argument to string.atol'
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return eval(sign + s + 'L', safe_env)
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# Left-justify a string
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def ljust(s, width):
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"""ljust(s, width) -> string
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Return a left-justified version of s, in a field of the
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specified width, padded with spaces as needed. The string is
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never truncated.
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"""
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n = width - len(s)
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if n <= 0: return s
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return s + ' '*n
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# Right-justify a string
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def rjust(s, width):
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"""rjust(s, width) -> string
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Return a right-justified version of s, in a field of the
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specified width, padded with spaces as needed. The string is
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never truncated.
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"""
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n = width - len(s)
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if n <= 0: return s
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return ' '*n + s
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# Center a string
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def center(s, width):
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"""center(s, width) -> string
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Return a center version of s, in a field of the specified
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width. padded with spaces as needed. The string is never
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truncated.
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"""
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n = width - len(s)
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if n <= 0: return s
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half = n/2
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if n%2 and width%2:
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# This ensures that center(center(s, i), j) = center(s, j)
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half = half+1
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return ' '*half + s + ' '*(n-half)
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# Zero-fill a number, e.g., (12, 3) --> '012' and (-3, 3) --> '-03'
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# Decadent feature: the argument may be a string or a number
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# (Use of this is deprecated; it should be a string as with ljust c.s.)
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def zfill(x, width):
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"""zfill(x, width) -> string
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Pad a numeric string x with zeros on the left, to fill a field
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of the specified width. The string x is never truncated.
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"""
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if type(x) == type(''): s = x
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else: s = `x`
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n = len(s)
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if n >= width: return s
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sign = ''
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if s[0] in ('-', '+'):
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sign, s = s[0], s[1:]
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return sign + '0'*(width-n) + s
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# Expand tabs in a string.
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# Doesn't take non-printing chars into account, but does understand \n.
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def expandtabs(s, tabsize=8):
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"""expandtabs(s [,tabsize]) -> string
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Return a copy of the string s with all tab characters replaced
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by the appropriate number of spaces, depending on the current
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column, and the tabsize (default 8).
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"""
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res = line = ''
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for c in s:
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if c == '\t':
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c = ' '*(tabsize - len(line)%tabsize)
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line = line + c
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if c == '\n':
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res = res + line
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line = ''
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return res + line
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# Character translation through look-up table.
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def translate(s, table, deletions=""):
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"""translate(s,table [,deletechars]) -> string
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Return a copy of the string s, where all characters occurring
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in the optional argument deletechars are removed, and the
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remaining characters have been mapped through the given
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translation table, which must be a string of length 256.
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"""
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if type(table) != type('') or len(table) != 256:
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raise TypeError, \
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"translation table must be 256 characters long"
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res = ""
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for c in s:
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if c not in deletions:
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res = res + table[ord(c)]
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return res
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# Capitalize a string, e.g. "aBc dEf" -> "Abc def".
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def capitalize(s):
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"""capitalize(s) -> string
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Return a copy of the string s with only its first character
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capitalized.
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"""
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return upper(s[:1]) + lower(s[1:])
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# Capitalize the words in a string, e.g. " aBc dEf " -> "Abc Def".
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# See also regsub.capwords().
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def capwords(s, sep=None):
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"""capwords(s, [sep]) -> string
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Split the argument into words using split, capitalize each
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word using capitalize, and join the capitalized words using
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join. Note that this replaces runs of whitespace characters by
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a single space.
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"""
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return join(map(capitalize, split(s, sep)), sep or ' ')
|
|
|
|
# Construct a translation string
|
|
_idmapL = None
|
|
def maketrans(fromstr, tostr):
|
|
"""maketrans(frm, to) -> string
|
|
|
|
Return a translation table (a string of 256 bytes long)
|
|
suitable for use in string.translate. The strings frm and to
|
|
must be of the same length.
|
|
|
|
"""
|
|
if len(fromstr) != len(tostr):
|
|
raise ValueError, "maketrans arguments must have same length"
|
|
global _idmapL
|
|
if not _idmapL:
|
|
_idmapL = map(None, _idmap)
|
|
L = _idmapL[:]
|
|
fromstr = map(ord, fromstr)
|
|
for i in range(len(fromstr)):
|
|
L[fromstr[i]] = tostr[i]
|
|
return joinfields(L, "")
|
|
|
|
# Substring replacement (global)
|
|
def replace(str, old, new, maxsplit=0):
|
|
"""replace (str, old, new[, maxsplit]) -> string
|
|
|
|
Return a copy of string str with all occurrences of substring
|
|
old replaced by new. If the optional argument maxsplit is
|
|
given, only the first maxsplit occurrences are replaced.
|
|
|
|
"""
|
|
return joinfields(splitfields(str, old, maxsplit), new)
|
|
|
|
|
|
# Try importing optional built-in module "strop" -- if it exists,
|
|
# it redefines some string operations that are 100-1000 times faster.
|
|
# It also defines values for whitespace, lowercase and uppercase
|
|
# that match <ctype.h>'s definitions.
|
|
|
|
try:
|
|
from strop import *
|
|
letters = lowercase + uppercase
|
|
except ImportError:
|
|
pass # Use the original, slow versions
|