cpython/Lib/string/__init__.py at main · python/cpython · GitHub

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"""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

"""

__all__ = ["ascii_letters", "ascii_lowercase", "ascii_uppercase", "capwords",

"digits", "hexdigits", "octdigits", "printable", "punctuation",

"whitespace", "Formatter", "Template"]

import _string

# 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 = r"""!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~"""

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. If the optional second argument sep is absent or None,

runs of whitespace characters are replaced by a single space

and leading and trailing whitespace are removed, otherwise

sep is used to split and join the words.

"""

return (sep or ' ').join(map(str.capitalize, s.split(sep)))

####################################################################

_sentinel_dict = {}

class _TemplatePattern:

# This descriptor is overwritten in ``Template._compile_pattern()``.

def __get__(self, instance, cls=None):

if cls is None:

return self

return cls._compile_pattern()

_TemplatePattern = _TemplatePattern()

class Template:

"""A string class for supporting $-substitutions."""

delimiter = '$'

# r'[a-z]' matches to non-ASCII letters when used with IGNORECASE, but

# without the ASCII flag. We can't add re.ASCII to flags because of

# backward compatibility. So we use the ?a local flag and [a-z] pattern.

# See https://bugs.python.org/issue31672

idpattern = r'(?a:[_a-z][_a-z0-9]*)'

braceidpattern = None

flags = None # default: re.IGNORECASE

pattern = _TemplatePattern # use a descriptor to compile the pattern

def __init_subclass__(cls):

super().__init_subclass__()

cls._compile_pattern()

@classmethod

def _compile_pattern(cls):

import re # deferred import, for performance

# `pattern` may be the `_TemplatePattern` sentinel (not yet compiled), an

# already-compiled regular expression object (as documented), or a string

# regular expression. An already-compiled object is returned as-is; the

# other two are compiled and cached back on the class.

pattern = cls.__dict__.get('pattern', _TemplatePattern)

if isinstance(pattern, re.Pattern):

# re.compile() rejects flags on an already-compiled pattern.

return pattern

if pattern is _TemplatePattern:

delim = re.escape(cls.delimiter)

id = cls.idpattern

bid = cls.braceidpattern or cls.idpattern

pattern = fr"""

{delim}(?:

(?P<escaped>{delim}) | # Escape sequence of two delimiters

(?P<named>{id}) | # delimiter and a Python identifier

{{(?P<braced>{bid})}} | # delimiter and a braced identifier

(?P<invalid>) # Other ill-formed delimiter exprs

)

"""

if cls.flags is None:

cls.flags = re.IGNORECASE

pat = cls.pattern = re.compile(pattern, cls.flags | re.VERBOSE)

return pat

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(keepends=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, mapping=_sentinel_dict, /, **kws):

if mapping is _sentinel_dict:

mapping = kws

elif kws:

from collections import ChainMap

mapping = ChainMap(kws, mapping)

# 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:

return str(mapping[named])

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, mapping=_sentinel_dict, /, **kws):

if mapping is _sentinel_dict:

mapping = kws

elif kws:

from collections import ChainMap

mapping = ChainMap(kws, mapping)

# Helper function for .sub()

def convert(mo):

named = mo.group('named') or mo.group('braced')

if named is not None:

try:

return str(mapping[named])

except KeyError:

return mo.group()

if mo.group('escaped') is not None:

return self.delimiter

if mo.group('invalid') is not None:

return mo.group()

raise ValueError('Unrecognized named group in pattern',

self.pattern)

return self.pattern.sub(convert, self.template)

def is_valid(self):

for mo in self.pattern.finditer(self.template):

if mo.group('invalid') is not None:

return False

if (mo.group('named') is None

and mo.group('braced') is None

and mo.group('escaped') is None):

# If all the groups are None, there must be

# another group we're not expecting

raise ValueError('Unrecognized named group in pattern',

self.pattern)

return True

def get_identifiers(self):

ids = []

for mo in self.pattern.finditer(self.template):

named = mo.group('named') or mo.group('braced')

if named is not None and named not in ids:

# add a named group only the first time it appears

ids.append(named)

elif (named is None

and mo.group('invalid') is None

and mo.group('escaped') is None):

# If all the groups are None, there must be

# another group we're not expecting

raise ValueError('Unrecognized named group in pattern',

self.pattern)

return ids

########################################################################

# The Formatter class (PEP 3101).

# The overall parser is implemented in _string.formatter_parser.

# The field name parser is implemented in _string.formatter_field_name_split.

class Formatter:

"""See PEP 3101 for details and purpose of this class."""

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,

auto_arg_index=0):

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

# handle arg indexing when empty field first parts are given.

field_first, _ = _string.formatter_field_name_split(field_name)

if field_first == '':

if auto_arg_index is False:

raise ValueError('cannot switch from manual field '

'specification to automatic field '

'numbering')

field_name = str(auto_arg_index) + field_name

auto_arg_index += 1

elif isinstance(field_first, int):

if auto_arg_index:

raise ValueError('cannot switch from automatic field '

'numbering to manual field '

'specification')

# disable auto arg incrementing, if it gets

# used later on, then an exception will be raised

auto_arg_index = False

# 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, auto_arg_index = self._vformat(

format_spec, args, kwargs,

used_args, recursion_depth-1,

auto_arg_index=auto_arg_index)

# format the object and append to the result

result.append(self.format_field(obj, format_spec))

return ''.join(result), auto_arg_index

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 is None:

return value

elif conversion == 's':

return str(value)

elif conversion == 'r':

return repr(value)

elif conversion == 'a':

return ascii(value)

raise ValueError("Unknown conversion specifier {0!s}".format(conversion))

def parse(self, format_string):

"""

Return an iterable that contains tuples of the form

(literal_text, field_name, format_spec, conversion).

*field_name* can be None, in which case there's no object

to format and output; otherwise, it is looked up and

formatted with *format_spec* and *conversion*.

"""

return _string.formatter_parser(format_string)

def get_field(self, field_name, args, kwargs):

"""Find the object referenced by a given field name.

The field name *field_name* can be for instance "0.name"

or "lookup[3]". The *args* and *kwargs* arguments are

passed to get_value().

"""

first, rest = _string.formatter_field_name_split(field_name)

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

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