How to check if a key-value pair is present in a dictionary?

Question

Is there a smart pythonic way to check if there is an item (key,value) in a dict?

a={\'a\':1,\'b\':2,\'c\':3}
b={\'a\':1}
c={\'a\':2}

b in a:
--> True
c          


        

Answer 1

Using get:

# this doesn't work if `None` is a possible value
# but you can use a different sentinal value in that case
a.get('a') == 1

Using try/except:

# more verbose than using `get`, but more foolproof also
a = {'a':1,'b':2,'c':3}
try:
    has_item = a['a'] == 1
except KeyError:
    has_item = False

print(has_item)

Other answers suggesting items in Python3 and viewitems in Python 2.7 are easier to read and more idiomatic, but the suggestions in this answer will work in both Python versions without any compatibility code and will still run in constant time. Pick your poison.