dictionary changed size during iteration
时间: 2024-05-12 14:20:27 浏览: 22
This error occurs in Python when you try to modify a dictionary while iterating over it. When you add or remove items from a dictionary during iteration, the size of the dictionary changes and the iterator becomes invalid. This can cause unexpected behavior or errors.
To avoid this error, you can create a copy of the dictionary before iterating over it, or use a different approach to modify the dictionary, such as adding the items to a new dictionary.
Here is an example of how this error can occur:
```
my_dict = {'a': 1, 'b': 2, 'c': 3}
for key, value in my_dict.items():
if key == 'b':
my_dict.pop(key) # Removing 'b' from the dictionary while iterating over it
```
In this example, the error message "RuntimeError: dictionary changed size during iteration" would be raised because we are removing an item from the dictionary while iterating over it.
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