python - 如何解决迭代错误期间字典更改大小？

Question

我想弹出字典中所有大值及其键，并保留最小值。这是我程序的一部分

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

结果

RuntimeError: dictionary changed size during iteration    

我怎样才能避免这个错误？

Answer 1

在Python3中，试试

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

当循环一个字典来更新它的键时，还有一件事应该小心:

代码1:

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

代码2:

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

code1/code2 的结果是:

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

我解决这个意外结果的方法:

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

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