[Python-Dev] Is implicit underscore assignment buggy?

Raymond Hettinger rhettinger at ewtllc.com
Wed Jun 7 21:23:44 CEST 2006

When the result of an expression is None, the interactive interpreter 
correctly suppresses the display of the result.  However, it also 
suppresses the underscore assignment.  I'm not sure if that is correct 
or desirable because a subsequent statement has no way of knowing 
whether the underscore assignment is current or whether it represents an 
earlier non-None result.

Here's an example from a co-worker's regular expression experiments:

 >>> import re, string
 >>> re.search('lmnop', string.letters)
<_sre.SRE_Match object at 0xb6f2c480>
 >>> re.search('pycon', string.letters)
 >>> if _ is not None:
...         print _.group()


More information about the Python-Dev mailing list