发布时间：2023-09-05 10:30
相关资料地址：gto76/python-cheatsheet: Comprehensive Python Cheatsheet (github.com)
目录
一、Dict的创建
1、dict的用法示例
（1）使用dict通过带参方式创建
（2）使用dict通过zip拼接方式来创建
2、dict.fromkeys的用法示例（生成所有键的值均为value的字典）
3、defaultdict的用法示例
二、Dict的元素添加、修改、删除
1、Dict的元素添加与修改
（1）直接添加与直接修改
（2）update的用法示例（使用update添加与修改）
2、Dict元素的删除
（1）pop的用法示例
三、Dict的元素查询
1、keys的用法示例（查询所有键）
2、values的用法示例（查询所有值）
3、items的用法示例
4、get的用法示例（根据key来获取值）
5、setdefault的用法示例
四、Dict的其他用法示例
1、生成相同value值的key集合
2、筛选对应key的键值对到新的字典中
示例：
= dict() # Creates a dict from coll. of key-value pairs.
= dict(zip(keys, values)) # Creates a dict from two collections.
= dict.fromkeys(keys [, value]) # Creates a dict from collection of keys.
= collections.defaultdict() # Creates a dict with default value of type.
= collections.defaultdict(lambda: 1) # Creates a dict with default value 1. 用法：
# = dict() # Creates a dict from coll. of key-value pairs.
# dict的通过带参方式创建
my_dict = dict(a=1, b=2)
print(my_dict)
# {'a': 1, 'b': 2} # = dict(zip(keys, values)) # Creates a dict from two collections.
# dict通过zip拼接来创建
keys = [0, 1, 2, 3]
values = ['a', 'b', 'c', 'd']
my_dict = dict(zip(keys, values))
print(my_dict)
# {0: 'a', 1: 'b', 2: 'c', 3: 'd'} # = dict.fromkeys(keys [, value]) # Creates a dict from collection of keys.
# 使用fromkeys创建默认值为value的字典
keys = [0, 1, 2, 3]
value = 'a'
my_dict = dict.fromkeys(keys, value)
print(my_dict)
# {0: 'a', 1: 'a', 2: 'a', 3: 'a'} 查询不存在key的时候
# defaultdict的用法
import collections
my_list = [1 ,2 ,3 ,4 ,5]
my_dict1 = collections.defaultdict(int)
my_dict2 = collections.defaultdict(list)
my_dict3 = collections.defaultdict(str)
my_dict4 = collections.defaultdict(set)
print(my_dict1)
print(my_dict2)
print(my_dict3)
print(my_dict4)
# defaultdict(, {})
# defaultdict(, {})
# defaultdict(, {})
# defaultdict(, {})
# 查询不存在的key
print(my_dict1[1])
print(my_dict2[1])
print(my_dict3[1])
print(my_dict4[1])
# 0
# []
#
# set() 示例：
.update() # Adds items. Replaces ones with matching keys.
value = .pop(key) # Removes item or raises KeyError. 用法：
# 直接添加
my_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e'}
my_dict[5] = 'f'
print(my_dict)
# {0: 'a', 1: 'b', 2: 'c', 3: 'd', 4: 'e', 5: 'f'}
# 直接修改
my_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e'}
my_dict[0] = 'f'
print(my_dict)
# {0: 'f', 1: 'b', 2: 'c', 3: 'd', 4: 'e'}# .update() # Adds items. Replaces ones with matching keys.
# update的用法1：更新最新key对应的值
my_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e'}
update_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'f'}
my_dict.update(update_dict)
print(my_dict)
# {0: 'a', 1: 'b', 2: 'c', 3: 'd', 4: 'f'}
# update的用法2：若有新的键值对，则更新新的键值对
my_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e'}
update_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e', 5:'f'}
my_dict.update(update_dict)
print(my_dict)
# {0: 'a', 1: 'b', 2: 'c', 3: 'd', 4: 'e', 5: 'f'}
# update的用法3：若更新空字典，则无改变
my_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e'}
update_dict = {}
my_dict.update(update_dict)
print(my_dict)
# {0: 'a', 1: 'b', 2: 'c', 3: 'd', 4: 'e'} # value = .pop(key) # Removes item or raises KeyError.
my_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e'}
my_dict.pop(0)
print(my_dict)
# {1: 'b', 2: 'c', 3: 'd', 4: 'e'} 示例：
= .keys() # Coll. of keys that reflects changes.
= .values() # Coll. of values that reflects changes.
= .items() # Coll. of key-value tuples that reflects chgs.
value = .get(key, default=None) # Returns default if key is missing.
value = .setdefault(key, default=None) # Returns and writes default if key is missing. 用法：
# = .keys() # Coll. of keys that reflects changes.
# keys的用法
my_dict = {0:'a', 1:'e', 2:'c', 4:'f', 3:'b'}
my_keys = my_dict.keys()
print(my_keys)
# dict_keys([0, 1, 2, 4, 3]) # = .values() # Coll. of values that reflects changes.
# values的用法
my_dict = {0:'a', 1:'e', 2:'c', 4:'f', 3:'b'}
my_values = my_dict.values()
print(my_values)
# dict_values(['a', 'e', 'c', 'f', 'b']) # = .items() # Coll. of key-value tuples that reflects chgs.
# items的用法
my_dict = {0:'a', 1:'e', 2:'c', 4:'f', 3:'b'}
my_items = my_dict.items()
print(my_items)
# dict_items([(0, 'a'), (1, 'e'), (2, 'c'), (4, 'f'), (3, 'b')])
# value = .get(key, default=None) # Returns default if key is missing.
# get的用法1
my_dict = {0:'a', 1:'e', 2:'c', 4:'f', 3:'b'}
my_value = my_dict.get(1)
print(my_value)
# e
# get的用法2
my_dict = {0:'a', 1:'e', 2:'c', 4:'f', 3:'b'}
my_value = my_dict.get(5)
print(my_value)
# None
my_value = my_dict.get(5, 'error')
print(my_value)
# error # value = .setdefault(key, default=None) # Returns and writes default if key is missing.
# setdefault的用法1：若存在key，则返回对应值
my_dict = {0:'a', 1:'e', 2:'c', 4:'f', 3:'b'}
my_value = my_dict.setdefault(3, 'h')
print(my_value)
print(my_dict)
# b
# {0: 'a', 1: 'e', 2: 'c', 4: 'f', 3: 'b'}
# setdefault的用法2：若不存在key，则添加对应值
my_dict = {0:'a', 1:'e', 2:'c', 4:'f', 3:'b'}
my_value = my_dict.setdefault(5, 'error')
print(my_value)
print(my_dict)
# {k for k, v in .items() if v == value} # Returns set of keys that point to the value.
# 生成相同value的key集合
my_dict = {0:'a', 1:'a', 2:'a', 3:'d', 4:'e'}
new_set = {k for k, v in my_dict.items() if v == 'a'}
print(new_set)
# {0, 1, 2} # {k: v for k, v in .items() if k in keys} # Returns a dictionary, filtered by keys.
# 筛选对应key的键值对到新的字典中
my_dict = {0:'a', 1:'b', 2:'c', 3:'d', 4:'e'}
keys = [0, 1, 2]
new_dict = {k:v for k, v in my_dict.items() if k in keys}
print(new_dict)
# {0: 'a', 1: 'b', 2: 'c'}