[Python-Dev] Is implicit underscore assignment buggy?

Raymond Hettinger raymond.hettinger at verizon.net
Wed Jun 7 23:49:23 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()

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