CODEWITHSUNDEEP
pythondictionary
Ozgur Vatansever
Ozgur Vatansever

Reputation: 52143

Remove more than one key from Python dict

Is there any efficient shortcut method to delete more than one key at a time from a python dictionary?

For instance;

x = {'a': 5, 'b': 2, 'c': 3}
x.pop('a', 'b')
print x
{'c': 3}

Upvotes: 6

Views: 7528

Answers (3)

kolypto
kolypto

Reputation: 35374

Remove a number of keys

I have tested the performance of three methods:

d = dict.fromkeys('abcdefghijklmnopqrstuvwxyz')
remove_keys = set('abcdef')

# Method 1
for key in remove_keys:
    del d[key]

# Method 2
for key in remove_keys:
    d.pop(key)

# Method 3
{key: v for key, v in d.items() if key not in remove_keys}

Here are the results of 1M iterations:

  1. 1.88s 1.9 ns/iter (100%)
  2. 2.41s 2.4 ns/iter (128%)
  3. 4.15s 4.2 ns/iter (221%)

So del is the fastest.

Remove a number of keys safely

However, if you want to delete safely, so that it does not fail with KeyError, you have to modify the code:

# Method 1
for key in remove_keys:
    if key in d:
        del d[key]

# Method 2
for key in remove_keys:
    d.pop(key, None)

# Method 3
{key: v for key, v in d.items() if key not in remove_keys}
  1. 2.03s 2.0 ns/iter (100%)
  2. 2.38s 2.4 ns/iter (117%)
  3. 4.11s 4.1 ns/iter (202%)

Still, del is the fastest.

Upvotes: 3

user688635
user688635

Reputation:

The general form I use is this:

  1. Produce a list of keys to delete from the mapping;
  2. Loop over the list and call del for each.

Example:

Say I want to delete all the string keys in a mapping. Produce a list of them:

>>> x={'a':5,'b':2,'c':3,1:'abc',2:'efg',3:'xyz'}
>>> [k for k in x if type(k) == str]
['a', 'c', 'b']

Now I can delete those:

>>> for key in [k for k in x if type(k) == str]: del x[key]
>>> x
{1: 'abc', 2: 'efg', 3: 'xyz'}

Upvotes: 2

vartec
vartec

Reputation: 134601

Use the del statement:

x = {'a': 5, 'b': 2, 'c': 3}
del x['a'], x['b']
print x
{'c': 3}

Upvotes: 14

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