9

I know that _s can be used as digit separator within numeric literals, between (groups of) digits, for instance 1_000 means 1000 and 0_0 means 00 or just 0. Today I accidentally typed a letter after the underscore, say 0_z. After pressing Enter, IPython showed the continuation prompt and the cursor: it expected more! But what? Example:

Python 3.12.7 (tags/v3.12.7:0b05ead, Oct  1 2024, 03:06:41) [MSC v.1941 64 bit (AMD64)]
Type 'copyright', 'credits' or 'license' for more information
IPython 8.31.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: 0_z
   ...:
   ...:
   ...: |

The vanilla Python prompt gives an expected syntax error instead:

Python 3.12.7 (tags/v3.12.7:0b05ead, Oct  1 2024, 03:06:41) [MSC v.1941 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> 0_z
  File "<stdin>", line 1
    0_z
     ^
SyntaxError: invalid decimal literal

Or course Ctrl+C gets me out of the problem. But exactly what (feature?) got me into it?

Improve this question
6
  • 3
    FYI it only happens since Python 3.12, with Python 3.11 there also is a syntax error. Commented Jan 7 at 13:26
  • There is the possibility it is a parser bug in iPython - I found no docs, (and no useful behavior) from this. Commented Jan 7 at 15:36
  • I'll ask around Commented Jan 7 at 15:55
  • My guess is there's an upcoming syntax change where this will be valid, and ipython has already implemented support for it. Commented Jan 7 at 16:12
  • 3
    @hpaulj you can, but that's not the point of the question. It is why that happens. Commented Jan 8 at 8:26
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