cpython/Lib/string.py

301 lines
10 KiB
Python

"""A collection of string constants.
Public module variables:
whitespace -- a string containing all ASCII whitespace
ascii_lowercase -- a string containing all ASCII lowercase letters
ascii_uppercase -- a string containing all ASCII uppercase letters
ascii_letters -- a string containing all ASCII letters
digits -- a string containing all ASCII decimal digits
hexdigits -- a string containing all ASCII hexadecimal digits
octdigits -- a string containing all ASCII octal digits
punctuation -- a string containing all ASCII punctuation characters
printable -- a string containing all ASCII characters considered printable
"""
# Some strings for ctype-style character classification
whitespace = ' \t\n\r\v\f'
ascii_lowercase = 'abcdefghijklmnopqrstuvwxyz'
ascii_uppercase = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
ascii_letters = ascii_lowercase + ascii_uppercase
digits = '0123456789'
hexdigits = digits + 'abcdef' + 'ABCDEF'
octdigits = '01234567'
punctuation = """!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~"""
printable = digits + ascii_letters + punctuation + whitespace
# Functions which aren't available as string methods.
# Capitalize the words in a string, e.g. " aBc dEf " -> "Abc Def".
def capwords(s, sep=None):
"""capwords(s, [sep]) -> string
Split the argument into words using split, capitalize each
word using capitalize, and join the capitalized words using
join. Note that this replaces runs of whitespace characters by
a single space.
"""
return (sep or ' ').join([x.capitalize() for x in s.split(sep)])
# Construct a translation map for bytes.translate
def maketrans(frm: bytes, to: bytes) -> bytes:
"""maketrans(frm, to) -> bytes
Return a translation table (a bytes object of length 256)
suitable for use in bytes.translate where each byte in frm is
mapped to the byte at the same position in to.
The strings frm and to must be of the same length.
"""
import warnings
warnings.warn("string.maketrans is deprecated, use bytes.maketrans instead",
DeprecationWarning, 2)
if len(frm) != len(to):
raise ValueError("maketrans arguments must have same length")
if not (isinstance(frm, bytes) and isinstance(to, bytes)):
raise TypeError("maketrans arguments must be bytes objects")
L = bytearray(range(256))
for i, c in enumerate(frm):
L[c] = to[i]
return bytes(L)
####################################################################
import re as _re
class _multimap:
"""Helper class for combining multiple mappings.
Used by .{safe_,}substitute() to combine the mapping and keyword
arguments.
"""
def __init__(self, primary, secondary):
self._primary = primary
self._secondary = secondary
def __getitem__(self, key):
try:
return self._primary[key]
except KeyError:
return self._secondary[key]
class _TemplateMetaclass(type):
pattern = r"""
%(delim)s(?:
(?P<escaped>%(delim)s) | # Escape sequence of two delimiters
(?P<named>%(id)s) | # delimiter and a Python identifier
{(?P<braced>%(id)s)} | # delimiter and a braced identifier
(?P<invalid>) # Other ill-formed delimiter exprs
)
"""
def __init__(cls, name, bases, dct):
super(_TemplateMetaclass, cls).__init__(name, bases, dct)
if 'pattern' in dct:
pattern = cls.pattern
else:
pattern = _TemplateMetaclass.pattern % {
'delim' : _re.escape(cls.delimiter),
'id' : cls.idpattern,
}
cls.pattern = _re.compile(pattern, _re.IGNORECASE | _re.VERBOSE)
class Template(metaclass=_TemplateMetaclass):
"""A string class for supporting $-substitutions."""
delimiter = '$'
idpattern = r'[_a-z][_a-z0-9]*'
def __init__(self, template):
self.template = template
# Search for $$, $identifier, ${identifier}, and any bare $'s
def _invalid(self, mo):
i = mo.start('invalid')
lines = self.template[:i].splitlines(True)
if not lines:
colno = 1
lineno = 1
else:
colno = i - len(''.join(lines[:-1]))
lineno = len(lines)
raise ValueError('Invalid placeholder in string: line %d, col %d' %
(lineno, colno))
def substitute(self, *args, **kws):
if len(args) > 1:
raise TypeError('Too many positional arguments')
if not args:
mapping = kws
elif kws:
mapping = _multimap(kws, args[0])
else:
mapping = args[0]
# Helper function for .sub()
def convert(mo):
# Check the most common path first.
named = mo.group('named') or mo.group('braced')
if named is not None:
val = mapping[named]
# We use this idiom instead of str() because the latter will
# fail if val is a Unicode containing non-ASCII characters.
return '%s' % (val,)
if mo.group('escaped') is not None:
return self.delimiter
if mo.group('invalid') is not None:
self._invalid(mo)
raise ValueError('Unrecognized named group in pattern',
self.pattern)
return self.pattern.sub(convert, self.template)
def safe_substitute(self, *args, **kws):
if len(args) > 1:
raise TypeError('Too many positional arguments')
if not args:
mapping = kws
elif kws:
mapping = _multimap(kws, args[0])
else:
mapping = args[0]
# Helper function for .sub()
def convert(mo):
named = mo.group('named')
if named is not None:
try:
# We use this idiom instead of str() because the latter
# will fail if val is a Unicode containing non-ASCII
return '%s' % (mapping[named],)
except KeyError:
return self.delimiter + named
braced = mo.group('braced')
if braced is not None:
try:
return '%s' % (mapping[braced],)
except KeyError:
return self.delimiter + '{' + braced + '}'
if mo.group('escaped') is not None:
return self.delimiter
if mo.group('invalid') is not None:
return self.delimiter
raise ValueError('Unrecognized named group in pattern',
self.pattern)
return self.pattern.sub(convert, self.template)
########################################################################
# the Formatter class
# see PEP 3101 for details and purpose of this class
# The hard parts are reused from the C implementation. They're exposed as "_"
# prefixed methods of str and unicode.
# The overall parser is implemented in str._formatter_parser.
# The field name parser is implemented in str._formatter_field_name_split
class Formatter:
def format(self, format_string, *args, **kwargs):
return self.vformat(format_string, args, kwargs)
def vformat(self, format_string, args, kwargs):
used_args = set()
result = self._vformat(format_string, args, kwargs, used_args, 2)
self.check_unused_args(used_args, args, kwargs)
return result
def _vformat(self, format_string, args, kwargs, used_args, recursion_depth):
if recursion_depth < 0:
raise ValueError('Max string recursion exceeded')
result = []
for literal_text, field_name, format_spec, conversion in \
self.parse(format_string):
# output the literal text
if literal_text:
result.append(literal_text)
# if there's a field, output it
if field_name is not None:
# this is some markup, find the object and do
# the formatting
# given the field_name, find the object it references
# and the argument it came from
obj, arg_used = self.get_field(field_name, args, kwargs)
used_args.add(arg_used)
# do any conversion on the resulting object
obj = self.convert_field(obj, conversion)
# expand the format spec, if needed
format_spec = self._vformat(format_spec, args, kwargs,
used_args, recursion_depth-1)
# format the object and append to the result
result.append(self.format_field(obj, format_spec))
return ''.join(result)
def get_value(self, key, args, kwargs):
if isinstance(key, int):
return args[key]
else:
return kwargs[key]
def check_unused_args(self, used_args, args, kwargs):
pass
def format_field(self, value, format_spec):
return format(value, format_spec)
def convert_field(self, value, conversion):
# do any conversion on the resulting object
if conversion == 'r':
return repr(value)
elif conversion == 's':
return str(value)
elif conversion is None:
return value
raise ValueError("Unknown converion specifier {0!s}".format(conversion))
# returns an iterable that contains tuples of the form:
# (literal_text, field_name, format_spec, conversion)
# literal_text can be zero length
# field_name can be None, in which case there's no
# object to format and output
# if field_name is not None, it is looked up, formatted
# with format_spec and conversion and then used
def parse(self, format_string):
return format_string._formatter_parser()
# given a field_name, find the object it references.
# field_name: the field being looked up, e.g. "0.name"
# or "lookup[3]"
# used_args: a set of which args have been used
# args, kwargs: as passed in to vformat
def get_field(self, field_name, args, kwargs):
first, rest = field_name._formatter_field_name_split()
obj = self.get_value(first, args, kwargs)
# loop through the rest of the field_name, doing
# getattr or getitem as needed
for is_attr, i in rest:
if is_attr:
obj = getattr(obj, i)
else:
obj = obj[i]
return obj, first