Question

my_dicts = [ 
    { 'key1' : 'value1',
      'key2' : 'value2' },

    { 'key1' : 'value1',  
      'key2' : 'value2' },

    { 'key1' : 'value1',  
      'key2' : 'value2' }]

用'value3'替换'value2'的所有实例的最有效方法是什么？

Answer 1

我没有做任何时间，但你可能不会比

好多了

for d in my_dicts:
    d.update((k, "value3") for k, v in d.iteritems() if v == "value2")

Python3的更新

for d in my_dicts:
    d.update((k, "value3") for k, v in d.items() if v == "value2")

Answer 2

var firstArray = ["k","d","r","r","p","k","b","p","k","k"]
var secondArray = ["k","d","r","s","d","r","b","c"]

let filterArray = firstArray.filter { secondArray.contains($0) }
let filterArray1 = firstArray.filter { !secondArray.contains($0) }
let filterIndex = firstArray.enumerated().filter { $0.element == "k" }.map { $0.offset }
print(filterArray) --> // ["k", "d", "r", "r", "k", "b", "k", "k"]
print(filterArray1) --> // ["p", "p"]
print(filterIndex) --> // [0, 5, 8, 9]

Answer 3

这是一个非常通用的答案，旨在处理大字典中多个值的多次出现。处理更简单的更具体的案例和/或使用小词典（如您的示例）可以更快地完成。

from collections import defaultdict

my_dicts = [
    { 'key1' : 'value1',
      'key2' : 'value2' },

    { 'key1' : 'value1',
      'key2' : 'value2',
      'key3' : 'value2'  }, # dup added for testing

    { 'key1' : 'value1',
      'key2' : 'value2' }]

def reverse(dct):
    """ Create dictionary mapping each value to list of one or more keys """
    ret = defaultdict(list)
    for key,val in dct.iteritems():
        ret[val].append(key)
    return ret

def replace_values(dicts, replacments):
    """ Replace values in each dict in dicts """
    for dct in dicts:
        revdict = reverse(dct)
        for oldval,newval in replacments.iteritems():
            for key in revdict.get(oldval, []):
                dct[key] = newval

replace_values(my_dicts, {'value2':'value3'})
print my_dicts
# [{'key2': 'value3', 'key1': 'value1'},
#  {'key3': 'value3', 'key2': 'value3', 'key1': 'value1'},
#  {'key2': 'value3', 'key1': 'value1'}]

Answer 4

Python3.7 dict理解（尽管会返回深层副本）：

update = {'key2':'value3'}
new_dicts = [{**d,**update} for d in my_dicts]

Answer 5

编辑：

或者

for item in my_dicts:
   item['key2'] = 'value3'

编辑词典列表中的值？

5 个答案: