user10756 user10756 - 1 month ago 5
Python Question

Python check that key is defined in dictionary

How to check that the key is defined in dictionary in python?

a={}
...
if 'a contains key b':
a[b] = a[b]+1
else
a[b]=1

Answer

Use the in operator:

if b in a:

Demo:

>>> a = {'foo': 1, 'bar': 2}
>>> 'foo' in a
True
>>> 'spam' in a
False

You really want to start reading the Python tutorial, the section on dictionaries covers this very subject.

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