python 字典fromskey

字典的fromkeys()方法用于创建一个新的字典，其中包含指定的键和相同的值。该方法的语法如下：

new_dict = {}.fromkeys(keys, value)

其中，keys是一个列表或可迭代对象，表示要作为字典的键的值；value是可选参数，表示要为所有键设置的值，默认为None。

以下是两种使用字典的fromkeys()方法的例子：

1. 使用列表作为键创建字典

name_list = ["fly1","fly2","fly3","fly1","fly2","fly3","fly1","fly2","fly3"]
new_name_dict = {}.fromkeys(name_list)
print(new_name_dict)

输出：

{'fly1': None, 'fly2': None, 'fly3': None}

2. 使用字符串作为键创建字典，并设置默认值

name_list = ["fly1","fly2","fly3","fly1","fly2","fly3","fly1","fly2","fly3"]
new_name_dict = {}.fromkeys(name_list, 0)
print(new_name_dict)

输出：

{'fly1': 0, 'fly2': 0, 'fly3': 0}