Inconsistency in fractions.Fraction() initialization error with invalid string

Bug description:

The fractions.Fraction() error message differs when, for example, 123.dd is done instead of 123.aa; they should be equal.

>>> from fractions import Fraction
>>> Fraction("123.dd")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    Fraction("123.dd")
  File "C:\Program Files\Python313\Lib\fractions.py", line 251, in __new__
    numerator = numerator * scale + int(decimal)
                                    ^^^^^^^^^^^^
ValueError: invalid literal for int() with base 10: 'dd'
>>> Fraction("123.aa")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    Fraction("123.aa")
  File "C:\Program Files\Python313\Lib\fractions.py", line 239, in __new__
    raise ValueError('Invalid literal for Fraction: %r' %
ValueError: Invalid literal for Fraction: '123.aa'

I discovered this bug while inspecting the rational parsing regex.

cpython/Lib/fractions.py

Lines 57 to 69 in dac1da2

    
           _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)

I think the bug stems from line 65's matching of d* instead of \d*.

CPython versions tested on:

3.13

Operating systems tested on:

Windows

Linked PRs

Add tests for invalid strings containing `d`

@mdickinson

@mdickinson fractions issue

Nice find! Agreed that this is a clear bug. Looks like it was introduced in #26422, so the bug is present in 3.11 onwards; the fix should be backported to 3.12 and 3.11.

gh-114014: Update `fractions.Fraction()`'s rational parsing regex (#1…

pythongh-114014: Update `fractions.Fraction()`'s rational parsing reg…

[3.12] gh-114014: Update `fractions.Fraction()`'s rational parsing re…

[3.11] gh-114014: Update `fractions.Fraction()`'s rational parsing re…

pythongh-114014: Update `fractions.Fraction()`'s rational parsing reg…

Navigation Menu

Repository navigation

Inconsistency in `fractions.Fraction()` initialization error with invalid string #114014

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

	_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)

Inconsistency in fractions.Fraction() initialization error with invalid string #114014

Description

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

Activity

terryjreedy commented on Jan 13, 2024

mdickinson commented on Jan 13, 2024

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions

Inconsistency in `fractions.Fraction()` initialization error with invalid string #114014