Float documentation doesn't allow int-like strings as valid arguments for float

[stevendaprano]

The documentation for float doesn't explicitly allow int-like strings, although it does give one as an example. E.g. although float('10') works and returns a float, the documentation implies that it shouldn't.

See discussion on Discuss.

Linked PRs

• gh-100428: Make int documentation more accurate #100436
• gh-100428: Make float documentation more accurate #100437
• [3.10] gh-100428: Make float documentation more accurate (GH-100437) #100510
• [3.11] gh-100428: Make float documentation more accurate (GH-100437) #100511
• [3.11] gh-100428: Make int documentation more accurate (GH-100436) #100674
• [3.10] gh-100428: Make int documentation more accurate (GH-100436) #100675

[mdickinson]

Maybe remove the indirection (the reference to floating-point literals) from the current documentation and give a direct description of what's permitted instead? That way the information is all in one place. The current documentation feels as though it was a shortcut taken for ease of documentation writing rather than ease of documentation reading.

On the other hand, it's definitely useful for users to know that any string that's acceptable as a floating-point literal is also acceptable as a string argument to float.

[mdickinson]

Another way in which the indirection is inaccurate is that float accepts arbitrary Unicode digits, while literals may only use ASCII digits:

>>> s = '６６６.０'
>>> float(s)
666.0
>>> eval(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1
    ６６６.０
    ^
SyntaxError: invalid character '６' (U+FF16)

[hauntsaninja]

There are inaccuracies in the int documentation too, for instance, the handling of leading zeros isn't really described. Also the following isn't correct:

Base 0 means to interpret exactly as a code literal

>>> s = "२३४५६७८९"
>>> int(s, 0)
23456789
>>> eval(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1
    २३४५६७८९
    ^
SyntaxError: invalid character '२' (U+0968)