Diez B. Roggisch wrote:
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?
Yes. Never use "is" unless you know 100% that you are talking about the same
object, not just equality.
Some objects are singletons, ie there's only ever one of them. The most
common singleton is None. In virtually every other case you should be
using "==" and "!=".
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