替换Python词典中的条目

Question

If I create a dictionary in Python,

x = {'a': {'b': 5, 'c': 6}, 'c':{'d': 10}}

and would like to replace one entry as follows:

x = {'a': {'b': 5, 'e': 4}, 'c':{'d': 10}}

How can I do that? Thanks!

Answer 1

What you want to do is not a replacement. It's two operations.

1. Delete c key from your dict: del x['a']['c']
2. Add a new value to the dic: x['a']['e']=4

To replace value of the same key, you just assign a new value to the key, x['a']['c']=15

Answer 2

You can use dictionary comprehension:

x = {'a': {'b': 5, 'c': 6}, 'c':{'d': 10}}
new_x = {a:{'e' if c == 'c' else c:4 if c == 'c' else d for c, d in b.items()} for a, b in x.items()} 

Output:

{'a': {'b': 5, 'e': 4}, 'c': {'d': 10}}

Or, using recursion to transverse a dictionary of unknown depth:

x = {'a': {'b': 5, 'c': 6}, 'c':{'d': 10}}
def update_dict(target, **to_become):
   return {a:{to_become.get(c, c):to_become['new_val'] if c in to_become else d for c, d in b.items()} if all(not isinstance(h, dict) for e, h in b.items()) else update_dict(b, **to_become) for a, b in target.items()}

print(update_dict(x, c = 'e', new_val = 4))

Output:

{'a': {'b': 5, 'e': 4}, 'c': {'d': 10}}