[Python] KeyError raised when trying to access a key in a dictionary - the key exists

I want to access the parts of this nested dictionary that have the 'leaf':'leaf' key-value pair:

tree={0: {'coords': [0],
'bounds': (0, 84),
'thres': 3e-08,
'id': 0,
'depol532_mean': 0.11638256238679075},
1: {'coords': [0, 0],
'bounds': (0, 54),
'thres': 3e-08,
'parent_id': 0,
'id': 1,
'depol532_mean': 0.13970860650679306,
'leaf': 'not_leaf'},
3: {'coords': [0, 0, 0],
'bounds': (0, 22),
'thres': 9.833542446299045e-07,
'parent_id': 1,
'id': 3,
'depol532_mean': 0.15483549951519165,
'leaf': 'leaf'},
4: {'coords': [0, 0, 1],
'bounds': (22, 54),
'thres': 9.833542446299045e-07,
'parent_id': 1,
'id': 4,
'depol532_mean': 0.1296008883894188,
'leaf': 'leaf'}}


Here is my code:

for node in tree:
#if tree[node]['parent_id']==1: this works - why doesnt the leaf thing?
if tree[node]['leaf']=='leaf':
print('its true!', node)
else:
print('nope!', node)


This yields a key error:

KeyError Traceback (most recent call last)
<ipython-input-14-eae55d0dcfe0> in <module>
2 for node in tree:
3 #if tree[node]['parent_id']==1: this works - why doesnt the leaf thing?
----> 4 if tree[node]['leaf']=='leaf':
5 print('nope!', node)
6 else:

KeyError: 'leaf'



I tried it with other elements of the dictionary, like the parent_id key, and that worked. I thought it could be something to do with the uniqueness of the entry, but it can't be that, because the parent_id is also not unique.

Maybe it's something to do with the fact the value is a string? I couldn't find much on this either though. I then tried editing the key-value pair by writing 'leaf': 1 for the leaf and 'leaf': 0 for not_leaf - but I still got the same error. So I guess it's a problem with the key part, not the value part.

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