cpython/Lib/string.py

285 lines
7.0 KiB
Python

# module 'string' -- A collection of string operations
# Warning: most of the code you see here isn't normally used nowadays.
# At the end of this file most functions are replaced by built-in
# functions imported from built-in module "strop".
# Some strings for ctype-style character classification
whitespace = ' \t\n\r\v\f'
lowercase = 'abcdefghijklmnopqrstuvwxyz'
uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
letters = lowercase + uppercase
digits = '0123456789'
hexdigits = digits + 'abcdef' + 'ABCDEF'
octdigits = '01234567'
# Case conversion helpers
_idmap = ''
for i in range(256): _idmap = _idmap + chr(i)
_lower = _idmap[:ord('A')] + lowercase + _idmap[ord('Z')+1:]
_upper = _idmap[:ord('a')] + uppercase + _idmap[ord('z')+1:]
_swapcase = _upper[:ord('A')] + lowercase + _upper[ord('Z')+1:]
del i
# Backward compatible names for exceptions
index_error = ValueError
atoi_error = ValueError
atof_error = ValueError
atol_error = ValueError
# convert UPPER CASE letters to lower case
def lower(s):
res = ''
for c in s:
res = res + _lower[ord(c)]
return res
# Convert lower case letters to UPPER CASE
def upper(s):
res = ''
for c in s:
res = res + _upper[ord(c)]
return res
# Swap lower case letters and UPPER CASE
def swapcase(s):
res = ''
for c in s:
res = res + _swapcase[ord(c)]
return res
# Strip leading and trailing tabs and spaces
def strip(s):
i, j = 0, len(s)
while i < j and s[i] in whitespace: i = i+1
while i < j and s[j-1] in whitespace: j = j-1
return s[i:j]
# Split a string into a list of space/tab-separated words
# NB: split(s) is NOT the same as splitfields(s, ' ')!
def split(s, sep=None):
if sep is not None: return splitfields(s, sep)
res = []
i, n = 0, len(s)
while i < n:
while i < n and s[i] in whitespace: i = i+1
if i == n: break
j = i
while j < n and s[j] not in whitespace: j = j+1
res.append(s[i:j])
i = j
return res
# Split a list into fields separated by a given string
# NB: splitfields(s, ' ') is NOT the same as split(s)!
# splitfields(s, '') returns [s] (in analogy with split() in nawk)
def splitfields(s, sep=None):
if sep is None: return split(s)
res = []
nsep = len(sep)
if nsep == 0:
return [s]
ns = len(s)
i = j = 0
while j+nsep <= ns:
if s[j:j+nsep] == sep:
res.append(s[i:j])
i = j = j + nsep
else:
j = j + 1
res.append(s[i:])
return res
# Join words with spaces between them
def join(words, sep = ' '):
return joinfields(words, sep)
# Join fields with optional separator
def joinfields(words, sep = ' '):
res = ''
for w in words:
res = res + (sep + w)
return res[len(sep):]
# Find substring, raise exception if not found
def index(s, sub, i = 0):
res = find(s, sub, i)
if res < 0:
raise ValueError, 'substring not found in string.index'
return res
# Find last substring, raise exception if not found
def rindex(s, sub, i = 0):
res = rfind(s, sub, i)
if res < 0:
raise ValueError, 'substring not found in string.index'
return res
# Count non-overlapping occurrences of substring
def count(s, sub, i = 0):
if i < 0: i = max(0, i + len(s))
n = len(sub)
m = len(s) + 1 - n
if n == 0: return m-i
r = 0
while i < m:
if sub == s[i:i+n]:
r = r+1
i = i+n
else:
i = i+1
return r
# Find substring, return -1 if not found
def find(s, sub, i = 0):
if i < 0: i = max(0, i + len(s))
n = len(sub)
m = len(s) + 1 - n
while i < m:
if sub == s[i:i+n]: return i
i = i+1
return -1
# Find last substring, return -1 if not found
def rfind(s, sub, i = 0):
if i < 0: i = max(0, i + len(s))
n = len(sub)
m = len(s) + 1 - n
r = -1
while i < m:
if sub == s[i:i+n]: r = i
i = i+1
return r
# Convert string to float
def atof(str):
import regex
sign = ''
s = str
if s and s[0] in '+-':
sign = s[0]
s = s[1:]
if not s:
raise ValueError, 'non-float argument to string.atof'
while s[0] == '0' and len(s) > 1 and s[1] in digits: s = s[1:]
if regex.match('[0-9]*\(\.[0-9]*\)?\([eE][-+]?[0-9]+\)?', s) != len(s):
raise ValueError, 'non-float argument to string.atof'
try:
return float(eval(sign + s))
except SyntaxError:
raise ValueError, 'non-float argument to string.atof'
# Convert string to integer
def atoi(str, base=10):
if base != 10:
# We only get here if strop doesn't define atoi()
raise ValueError, "this string.atoi doesn't support base != 10"
sign = ''
s = str
if s and s[0] in '+-':
sign = s[0]
s = s[1:]
if not s:
raise ValueError, 'non-integer argument to string.atoi'
while s[0] == '0' and len(s) > 1: s = s[1:]
for c in s:
if c not in digits:
raise ValueError, 'non-integer argument to string.atoi'
return eval(sign + s)
# Convert string to long integer
def atol(str, base=10):
if base != 10:
# We only get here if strop doesn't define atol()
raise ValueError, "this string.atol doesn't support base != 10"
sign = ''
s = str
if s and s[0] in '+-':
sign = s[0]
s = s[1:]
if not s:
raise ValueError, 'non-integer argument to string.atol'
while s[0] == '0' and len(s) > 1: s = s[1:]
for c in s:
if c not in digits:
raise ValueError, 'non-integer argument to string.atol'
return eval(sign + s + 'L')
# Left-justify a string
def ljust(s, width):
n = width - len(s)
if n <= 0: return s
return s + ' '*n
# Right-justify a string
def rjust(s, width):
n = width - len(s)
if n <= 0: return s
return ' '*n + s
# Center a string
def center(s, width):
n = width - len(s)
if n <= 0: return s
half = n/2
if n%2 and width%2:
# This ensures that center(center(s, i), j) = center(s, j)
half = half+1
return ' '*half + s + ' '*(n-half)
# Zero-fill a number, e.g., (12, 3) --> '012' and (-3, 3) --> '-03'
# Decadent feature: the argument may be a string or a number
# (Use of this is deprecated; it should be a string as with ljust c.s.)
def zfill(x, width):
if type(x) == type(''): s = x
else: s = `x`
n = len(s)
if n >= width: return s
sign = ''
if s[0] in ('-', '+'):
sign, s = s[0], s[1:]
return sign + '0'*(width-n) + s
# Expand tabs in a string.
# Doesn't take non-printing chars into account, but does understand \n.
def expandtabs(s, tabsize=8):
res = line = ''
for c in s:
if c == '\t':
c = ' '*(tabsize - len(line)%tabsize)
line = line + c
if c == '\n':
res = res + line
line = ''
return res + line
# Character translation through look-up table.
def translate(s, table):
if type(table) != type('') or len(table) != 256:
raise TypeError, "translation table must be 256-char string"
res = ""
for c in s:
res = res + table[ord(c)]
return res
# Capitalize a string, e.g. "aBc dEf" -> "Abc def".
def capitalize(s):
return upper(s[:1]) + lower(s[1:])
# Capitalize the words in a string, e.g. " aBc dEf " -> "Abc Def".
# See also regsub.capwords().
def capwords(s):
return join(map(capitalize, split(s)))
# 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