Numeric literal and whitespaces

Classification

Affected Components : builtin
Operating System : Linux
Python Versions : 2.6.x, 2.7.x
Reproducible : Yes

Source code

try:
    x = int('+ 0')
    print """OK: int('+ 0') - string converted"""
except Exception as e:
    print """KO: int('+ 0') - string not converted raise Error: """ + repr(e,)

try:
    y = float('+0.0')
    print """OK: float('+0.0') - string converted"""
except Exception as e:
    print """KO: float('+0.0') - string not converted raise Error: """ + repr(e,)

try:
    z = float('+ 0.0')
    print """OK: float('+ 0.0') - string converted"""
except Exception as e:
    print """KO: float('+ 0.0') - string not converted raise Error: """ + repr(e,)

try:
    a = int('2 3')
    print """OK: int('2 3') - string converted"""
except Exception as e:
    print """KO: int('2 3') - string not converted raise Error: """ + repr(e,)

try:
    import string
    b = string.atof("-2")
    print """OK: string.atof("-2") - string converted"""
except Exception as e:
    print """KO: string.atof("-2") - string not converted raise Error: """ + repr(e,)

try:
    import string
    c = string.atof("- 2")
    print """OK: string.atof("- 2") - string converted"""
except Exception as e:
    print """KO: string.atof("- 2") - string not converted raise Error: """ + repr(e,)

Steps to Produce/Reproduce

To reproduce the problem copy the source code in a file and execute the script using the following command syntax:

$ python -OOBRtt test.py

Alternatively you can open python in interactive mode:

$ python -OOBRtt <press enter>

Then copy the lines of code into the interpreter.

Description

Tests using Python 2.6 generated the following results:

OK: int('+ 0') - string converted
OK: float('+0.0') - string converted
KO: float('+ 0.0') - string not converted raise Error: ValueError('invalid literal for float(): + 0.0',)
KO: int('2 3') - string not converted raise Error: ValueError("invalid literal for int() with base 10: '2 3'",)
OK: string.atof("-2") - string converted
KO: string.atof("- 2") - string not converted raise Error: ValueError('invalid literal for float(): - 2',)

And tests using Python 2.7 generated the following results:

OK: int('+ 0') - string converted
OK: float('+0.0') - string converted
KO: float('+ 0.0') - string not converted raise Error: ValueError('could not convert string to float: + 0.0',)
KO: int('2 3') - string not converted raise Error: ValueError("invalid literal for int() with base 10: '2 3'",)
OK: string.atof("-2") - string converted
KO: string.atof("- 2") - string not converted raise Error: ValueError('could not convert string to float: - 2',)

In python whitespace between sign and digits should be always discarded but is not the case as the behaviour changes depending on the object type.

For numbers expressed as int whitespace is discarded while for numbers expressed as float whitespace is NOT discarded.

Also to note that whitespace between integers like (2 3) never works regardless of the object type.

Workaround

We are not aware on any easy solution other than trying to avoid using numeric literals for cases like the one examined, instead the code should handle specific implementation and stripe leading and trailing whitespaces and unprintable characters by default.