The documentation of int(x) and int(x, base=10) specifies:
“If x is not a number or if base is given, then x must be a string, bytes, or bytearray instance representing an integer in radix base. Optionally, the string can be preceded by + or - (with no space in between), have leading zeros, be surrounded by whitespace, and have single underscores interspersed between digits.”
https://docs.python.org/3/library/functions.html?#int
The Python 2 documentation is similar:
https://docs.python.org/2.7/library/functions.html?#int
int('+␣42') is valid or not?
The Python 3 implementation (at least from 3.5.9 to 3.11.0) reject spaces between the sign and the integer. That is the expected behaviour by the documentation.
But spaces between the sign and the integer are valid for Pypy 3.7, Python 2.7, Pypy 2.7 and Jython 2.7!
Is it really a bug or is there no really a precise specification and it is implementation dependent?
I expected that implementations raise a ValuerError for these kind of values.
float('+␣42') is rejected by all implementations.
The expected behavior, by Python 3:
Python 3.9.2 (default, Feb 28 2021, 17:03:44)
[GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> int('+ 42')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '+ 42'
>>> int('- 42')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '- 42'
>>> float('+ 42')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '+ 42'
See https://gcc.godbolt.org/z/ETe731KPj to try other Python 3 versions.
The unexpected behavior, by Pypy 3, Python 2, Pypy 2 and Jython 2:
Python 3.7.10 (7.3.5+dfsg-2+deb11u2, Nov 01 2022, 20:16:36)
[PyPy 7.3.5 with GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>> int('+ 42')
42
>>>> int('- 42')
-42
>>>> float('+ 42')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '+ 42'
Python 2.7.18 (default, Jul 14 2021, 08:11:37)
[GCC 10.2.1 20210110] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> int('+ 42')
42
>>> int('- 42')
-42
>>> float('+ 42')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: + 42
Python 2.7.18 (7.3.3+dfsg-2, May 02 2021, 15:10:01)
[PyPy 7.3.3 with GCC 10.2.1 20210110] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>> int('+ 42')
42
>>>> int('- 42')
-42
>>>> float('+ 42')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '+ 42'
Jython 2.7.2-DEV (uncontrolled:+, Jan 3 1970, 22:46:05)
[OpenJDK 64-Bit Server VM (Debian)] on java11.0.18
Type "help", "copyright", "credits" or "license" for more information.
>>> int('+ 42')
42
>>> int('- 42')
-42
>>> float('+ 42')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: invalid literal for float: + 42