python 快速创建字典 fromkes()

作用：快速创建字典

特点：共用value

seq = ['google', 'ie', 'firefox']
# seq为可迭代对象（str, list, tuple, dict, set）
dic = dict.fromkeys(seq)
print(dic)      # {'google': None, 'ie': None, 'firefox': None}

dic2 = dict.fromkeys(seq, 10)
print(dic2)     # {'google': 10, 'ie': 10, 'firefox': 10}