Python – What happens if I delete a non-existent key in the Python dictionary class?

Suppose buff is a dictionary. I execute del buff[k], but k is not a key in buff. Is this a bug, or is your python just passing the line like nothing happened?

Let’s test it:

>>> buff={1:2,4:5}
>>> del buff[1]
>>> del buff[6]
Traceback (most recent call last):
  File "<string>", line 301, in runcode
  File "<interactive input>", line 1, in <module>
KeyError: 6

But in this case, del has nothing to do with it. Using the [] symbol to access a key that does not exist in the dictionary throws a KeyError

Note that it is better to use buff.pop(k) (in this case, the delete operation triggers KeyError, the result is the same if it does not exist).

To create a method that doesn’t crash/fail-safe, simply do the following:

if k in buff:
    buff.pop(k)

Or (it’s better to ask for forgiveness than for permission):

try:
   buff.pop(k)
except KeyError:
   pass