How to remove all null elements from a dictionary?

Question

Python

There is a dictionary like: {user1 { var1: 2, var2: 0, var3: 1, var4: 0}, user2 {var1: 0, var2: 1, var3: 0, var4: 0}, user3{ var1:1, var2 : 0, var3:0, var4:0}}
How to remove all "subdictionary" keys with null values, so that it turns out:
{user1 { var1: 2, var3: 1}, user2 {var2: 1}, user3{ var1:1}}.
I tried, but I could only implement the function where the user is passed. Such an implementation is unacceptable. the number of users is large.
PS There would be no problems if the dictionary was "one-dimensional"

Answer 1

You need to go through it recursively.

>>> def f(d):
...     for i in set(d):
...         e = d[i]
...         if isinstance(e, dict):
...             f(e)
...         elif e == 0:
...             del d[i]
... 
>>> d = {'user1': {'var1': 2,
...                'var2': 0,
...                'var3': 1,
...                'var4': 0},
...      'user2': {'var1': 0,
...                'var2': 1,
...                'var3': 0,
...                'var4': 0},
...      'user3': {'var1': 1,
...                'var2': 0,
...                'var3': 0,
...                'var4': 0}}
>>> 
>>> f(d)
>>> d
{'user3': {'var1': 1}, 'user2': {'var2': 1}, 'user1': {'var1': 2, 'var3': 1}}
>>>