python dict常用

本文主要是python中dict常用的方法：

1. list 转化为 dict

2. dict遍历删除指定条件的元素

3. dict安装key或者value排序

4. dict的value统计计数

---

两个list转化为dict

def lst_2_dict():    """    combine two list to dict    :return:    """    lst1 = ['a', 'b', 'c']    lst2 = [1, 2, 3]    # d = {k: v for k, v in zip(lst1, lst2)}    d = dict(zip(lst1, lst2))    print d    # {'a': 1, 'c': 3, 'b': 2}

删除dict中value < 0 的元素

def iter_dict_remove():    """remove item in dict while iteration it"""    d_info = {'aa': -1, 'bb': 0, 'cc': 1, 'dd': 2}    for k in d_info.keys():        print k, d_info[k]        if d_info[k] < 0:            del d_info[k]    print 'after del', d_info 

按照key的顺序变量dict

def iter_dic_sort():    """iter dict by sorted keys"""    d_info = {'33': 33, '88': 88, '22': 22, '44': 44}    for k in sorted(d_info):        print k, d_info[k]

安装key或者value对dict排序:

def dict_sort_by_value():    dic_num = {'first': 11, 'second': 2, 'third': 33, 'Fourth': 4}    # print all the keys    print dic_num.keys()    print list(dic_num)    # ['second', 'Fourth', 'third', 'first']    # print all the sorted keys    print sorted(dic_num)    # ['Fourth', 'first', 'second', 'third']    print sorted(dic_num, key=str.lower)    # ['first', 'Fourth', 'second', 'third']    # print sorted values    print sorted(dic_num.values())    # [2, 4, 11, 33]    # sorted by value    sorted_val = sorted(dic_num.items(), key=operator.itemgetter(1))    # [('second', 2), ('Fourth', 4), ('first', 11), ('third', 33)]    print sorted_val    # sorted by key    sorted_key = sorted(dic_num.items(), key=operator.itemgetter(0))    print sorted_key    # [('Fourth', 4), ('first', 11), ('second', 2), ('third', 33)]    dic_k_lst = {'11': [1, 2], 'ab': [3], 'cd': [0, -1, 2]}    # Sort a dictionary by length of the value    print sorted(dic_k_lst.items(), key=lambda item: len(item[1]))    # [('ab', [3]), ('11', [1, 2]), ('cd', [0, -1, 2])]    dic_k_set = {'11': {1, 2}, 'ab': {3}, 'cd': {0, -1, 2}}    # Sort a dictionary by length of the value    d_val_len = sorted(dic_k_set.items(), key=lambda item: len(item[1]))    print d_val_len    # [('ab', set([3])), ('11', set([1, 2])), ('cd', set([0, 2, -1]))]    print d_val_len[0][1]    # set([3])    print len(d_val_len[0][1])    # 1 (长度为 1)

对dict的value计数:

def dic_count_value():    from collections import Counter    dic_k_lst = {'11': None, 'ab': 3, 'name': 'xy', 'none': None, 'age': 26}    print Counter(dic_k_lst.values())    # Counter({None: 2, 'xy': 1, 26: 1, 3: 1})    # 统计none与非none的数量    count_none = 0    count_not_none = 0    for k in dic_k_lst.keys():        if dic_k_lst[k] is None:            count_none += 1        else:            count_not_none += 1    print count_none, count_not_none    # 2 3

统计dict中每个list的长度：

def count_val_lst_len():    d = {'T1': ['eggs', 'bacon', 'sausage'], 'T2': ['spam', 'ham', 'monty', 'python']}    print map(len, d.values())    # [4, 3]    print sum(map(len, d.values()))    # 7

dict value求和:

def sum_dic_val():    d_info = {'33': 1, '88': 2, '22': 3, '44': 4}    print sum(d_info.values())    # 10

def dic_probability():    p = {1: {1: 0.1, 2: 0.3}, 2: {1: 0.1, 2: 0.3}}    # {1: {1: 0.1, 2: 0.3}, 2: {1: 0.1, 2: 0.3}}    print p[2], p[2][2]    # {1: 0.1, 2: 0.3} 0.3

具体见本人的github

参考：

https://stackoverflow.com/questions/613183/how-to-sort-a-dictionary-by-value

https://stackoverflow.com/questions/72899/how-do-i-sort-a-list-of-dictionaries-by-values-of-the-dictionary-in-python

http://pythoncentral.io/how-to-sort-python-dictionaries-by-key-or-value/

https://stackoverflow.com/questions/20464368/sort-a-dictionary-by-length-of-the-value