cpython/Lib/string.py

279 lines
9.5 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)])
####################################################################
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