python - How to solve dictionary changed size during iteration error?

Question

I want pop out all the large values and its keys in a dictionary, and keep the smallest. Here is the part of my program

for key,value in dictionary.items():
    for key1, value1 in dictionary.items(): 
            if key1!= key and value > value1:
                dictionary.pop(key)             
    print (dictionary)  

Which results in

RuntimeError: dictionary changed size during iteration    

How can I avoid this error?

Answer 1

In Python3, Try

for key in list(dict.keys()):
    if condition:
        matched
        del dict[key]

1 more thing should be careful when looping a dict to update its key:

Code1:

keyPrefix = ‘keyA’
for key, value in Dict.items():
    newkey = ‘/’.join([keyPrefix, key])
    Dict[newkey] = Dict.pop(key)

Code2:

keyPrefix = ‘keyA’
for key, value in Dict.keys():
    newkey = ‘/’.join([keyPrefix, key])
    Dict[newkey] = Dict.pop(key)

Result of code1/code2 is:

{‘keyA/keyA/keyB’ : ”, ‘keyA/keyA/keyA’: ”}

My way to resolve this unexpected result:

    Dict = {‘/’.join([keyPrefix, key]): value for key, value in Dict.items()}

Link: https://blog.gainskills.top/2016/07/21/loop-a-dict-to-update-key/