May 1, 2025 · May 14, 2025 · May 15, 2025 · May 16, 2025 · May 19, 2025 · May 19, 2025
diff --git a/Lib/fractions.py b/Lib/fractions.py
    result = hash_ if numerator >= 0 else -hash_
    return -2 if result == -1 else result

 _RATIONAL_FORMAT = re.compile(r"""
    \A\s*                                  # optional whitespace at the start,
    (?P<sign>[-+]?)                        # an optional sign, then
    (?=\d|\.\d)                            # lookahead for digit or .digit
    (?P<num>\d*|\d+(_\d+)*)                # numerator (possibly empty)
    (?:                                    # followed by
       (?:\s*/\s*(?P<denom>\d+(_\d+)*))?   # an optional denominator
    |                                      # or
       (?:\.(?P<decimal>\d*|\d+(_\d+)*))?  # an optional fractional part
       (?:E(?P<exp>[-+]?\d+(_\d+)*))?      # and optional exponent
    )
    \s*\z                                  # and optional whitespace to finish
 """, re.VERBOSE | re.IGNORECASE)


 # Helpers for formatting


            elif isinstance(numerator, str):
                # Handle construction from strings.
                m = _RATIONAL_FORMAT.match(numerator)
                if m is None:
                    raise ValueError('Invalid literal for Fraction: %r' %
                                     numerator)
                numerator = int(m.group('num') or '0')
                denom = m.group('denom')
                if denom:
                    denominator = int(denom)
                else:
                    denominator = 1
                    decimal = m.group('decimal')
                    if decimal:
                        decimal = decimal.replace('_', '')
                        scale = 10**len(decimal)
                        numerator = numerator * scale + int(decimal)
                        denominator *= scale
                    exp = m.group('exp')
                    if exp:
                        exp = int(exp)
                        if exp >= 0:
                            numerator *= 10**exp
                fraction_literal = numerator
                num, is_fraction_format, denom = fraction_literal.partition('/')
                try:
                    num = num.strip()
                    denom = denom.strip()
                    if num and denom and denom[0].isdigit():
                        denominator = int(denom)
                        numerator = int(num)
                    elif num and not is_fraction_format:
                        denominator = 1
                        num, is_exp_format, exp = num.replace('E', 'e').partition('e')
                        if is_exp_format and not exp:
                            raise ValueError
                        num, _, decimal = num.partition('.')
                        if num:
                            if num[0] in ('+', '-'):
                                sign = num[0] == '-'
                                num = num[1:]
                            else:
                                sign = 0
                            if num and not (num[-1].isdigit() and num[0].isdigit()):
                                raise ValueError
                        else:
                            denominator *= 10**-exp
                if m.group('sign') == '-':
                    numerator = -numerator
                            sign = 0
                        if decimal:
                            if not decimal[0].isdigit() or not decimal[-1].isdigit():
                                raise ValueError
                            numerator = int(num or '0')
                            decimal_len = len(decimal.replace('_', ''))
                            decimal = int(decimal)
                            scale = 10**decimal_len
                            numerator = numerator*scale + decimal
                            denominator *= scale
                        else:
                            numerator = int(num)
                        if sign:
                            numerator = -numerator
                        if exp:
                            if not (exp[0] in ('+', '-') or exp[0].isdigit()):
                                raise ValueError
                            exp = int(exp)
                            if exp >= 0:
                                numerator *= 10**exp
                            else:
                                denominator *= 10**-exp
                    else:
                        raise ValueError
                except ValueError as exc:
                    if exc.args and re.match('^Exceeds', exc.args[0]):
                        raise
                    raise ValueError('Invalid literal for Fraction: %r' %
                                     fraction_literal)

            else:
                raise TypeError("argument should be a string or a Rational "
diff --git a/Lib/test/test_fractions.py b/Lib/test/test_fractions.py
        # Imitate float's parsing.
        check_invalid("+ 3/2")
        check_invalid("- 3/2")
        check_invalid("+ 343.33")
        # Avoid treating '.' as a regex special character.
        check_invalid("3a2")
        # Don't accept combinations of decimals and rationals.
        # No space around e.
        check_invalid("3.2 e1")
        check_invalid("3.2e 1")
        check_invalid("232e\t2")
        # Fractional part don't need a sign.
        check_invalid("3.+2")
        check_invalid("3.-2")
diff --git a/Misc/NEWS.d/next/Library/2025-05-02-13-30-08.gh-issue-72902.B0BV8C.rst b/Misc/NEWS.d/next/Library/2025-05-02-13-30-08.gh-issue-72902.B0BV8C.rst
 Improve speed (x1.3-1.5) of the :class:`~fractions.Fraction` constructor for
 string inputs.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -53,20 +53,6 @@ def _hash_algorithm(numerator, denominator):
		result = hash_ if numerator >= 0 else -hash_
		return -2 if result == -1 else result

		_RATIONAL_FORMAT = re.compile(r"""
		\A\s* # optional whitespace at the start,
		(?P<sign>[-+]?) # an optional sign, then
		(?=\d\|\.\d) # lookahead for digit or .digit
		(?P<num>\d\|\d+(_\d+)) # numerator (possibly empty)
		(?: # followed by
		(?:\s/\s(?P<denom>\d+(_\d+)*))? # an optional denominator
		\| # or
		(?:\.(?P<decimal>\d\|\d+(_\d+)))? # an optional fractional part
		(?:E(?P<exp>[-+]?\d+(_\d+)*))? # and optional exponent
		)
		\s*\z # and optional whitespace to finish
		""", re.VERBOSE \| re.IGNORECASE)


		# Helpers for formatting

Expand DownExpand Up		@@ -252,31 +238,58 @@ def __new__(cls, numerator=0, denominator=None):

		elif isinstance(numerator, str):
		# Handle construction from strings.
		m = _RATIONAL_FORMAT.match(numerator)
		if m is None:
		raise ValueError('Invalid literal for Fraction: %r' %
		numerator)
		numerator = int(m.group('num') or '0')
		denom = m.group('denom')
		if denom:
		denominator = int(denom)
		else:
		denominator = 1
		decimal = m.group('decimal')
		if decimal:
		decimal = decimal.replace('_', '')
		scale = 10**len(decimal)
		numerator = numerator * scale + int(decimal)
		denominator *= scale
		exp = m.group('exp')
		if exp:
		exp = int(exp)
		if exp >= 0:
		numerator = 10*exp
		fraction_literal = numerator
		num, is_fraction_format, denom = fraction_literal.partition('/')
		try:
		num = num.strip()
		denom = denom.strip()
		if num and denom and denom[0].isdigit():
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		denominator = int(denom)
		numerator = int(num)
		elif num and not is_fraction_format:
		denominator = 1
		num, is_exp_format, exp = num.replace('E', 'e').partition('e')
		if is_exp_format and not exp:
		raise ValueError
		num, _, decimal = num.partition('.')
		if num:
		if num[0] in ('+', '-'):
		sign = num[0] == '-'
		num = num[1:]
		else:
		sign = 0
		if num and not (num[-1].isdigit() and num[0].isdigit()):
		raise ValueError
		else:
		denominator = 10*-exp
		if m.group('sign') == '-':
		numerator = -numerator
		sign = 0
		if decimal:
		if not decimal[0].isdigit() or not decimal[-1].isdigit():
		raise ValueError
		numerator = int(num or '0')
		decimal_len = len(decimal.replace('_', ''))
		decimal = int(decimal)
		scale = 10**decimal_len
		numerator = numerator*scale + decimal
		denominator *= scale
		else:
		numerator = int(num)
		if sign:
		numerator = -numerator
		if exp:
		if not (exp[0] in ('+', '-') or exp[0].isdigit()):
		raise ValueError
		exp = int(exp)
		if exp >= 0:
		numerator = 10*exp
		else:
		denominator = 10*-exp
		else:
		raise ValueError
		except ValueError as exc:
		if exc.args and re.match('^Exceeds', exc.args[0]):
		raise
		raise ValueError('Invalid literal for Fraction: %r' %
		fraction_literal)

		else:
		raise TypeError("argument should be a string or a Rational "
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -434,6 +434,7 @@ def check_invalid(s):
		# Imitate float's parsing.
		check_invalid("+ 3/2")
		check_invalid("- 3/2")
		check_invalid("+ 343.33")
		# Avoid treating '.' as a regex special character.
		check_invalid("3a2")
		# Don't accept combinations of decimals and rationals.
Expand All		@@ -445,6 +446,7 @@ def check_invalid(s):
		# No space around e.
		check_invalid("3.2 e1")
		check_invalid("3.2e 1")
		check_invalid("232e\t2")
		# Fractional part don't need a sign.
		check_invalid("3.+2")
		check_invalid("3.-2")
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Improve speed (x1.3-1.5) of the :class:`~fractions.Fraction` constructor for
		string inputs.