mk wrote:
Hello everyone,
print hosts
hosts = [ s.strip() for s in hosts if s is not '' and s is not None
and s is not '\n' ]
print hosts
['9.156.44.227\n', '9.156.46.34 \n', '\n']
['9.156.44.227', '9.156.46.34', '']
Why does the hosts list after list comprehension still contain '' in
last position?
I checked that:
print hosts
hosts = [ s.strip() for s in hosts if s != '' and s != None and s !=
'\n' ]
print hosts
..works as expected:
['9.156.44.227\n', '9.156.46.34 \n', '\n']
['9.156.44.227', '9.156.46.34']
Are there two '\n' strings in the interpreter's memory or smth so the
identity check "s is not '\n'" does not work as expected?
This is weird. I expected that at all times there is only one '\n'
string in Python's cache or whatever that all labels meant by the
programmer as '\n' string actually point to. Is that wrong assumption?
Clearly. And even if you do figure out what the internals really are
doing, it is foolish to write a program that depends on them -- there is
no guarantee that such implementation specific behavior will be
consistent over other implementations.
Conclusion: Don't use "is" for comparison when you mean to check for
equality. And you do want an equality check here.
Gary Herron
Regards,
mk
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