1, enumerate(可迭代对象, index_base)
from collections.abc import Iterator my_list = ["aa", "b", "c"] result = enumerate(my_list) # 迭代器: 每次返回一个元组, tuple(index, value) print(type(result)) # <class 'enumerate'> print(isinstance(result, Iterator)) # True
遍历1：for后面跟1个变量
for i in result: print(type(i), i)
运行结果：
<class 'tuple'> (0, 'aa')
<class 'tuple'> (1, 'b')
<class 'tuple'> (2, 'c')
遍历2：for后面跟多个变量
for i, v in result: print(type(i), i, type(v), v)
运行结果：
<class 'int'> 0 <class 'str'> aa
<class 'int'> 1 <class 'str'> b
<class 'int'> 2 <class 'str'> c
from collections.abc import Iterator my_list = ["aa", "b", "c"] index_base = 123 result = enumerate(my_list, index_base) # 迭代器: 每次返回一个元组, tuple(index, value) print(type(result)) # <class 'enumerate'> print(isinstance(result, Iterator)) # True for i, v in result: print(type(i), i, type(v), v)
运行结果：
<class 'int'> 123 <class 'str'> aa
<class 'int'> 124 <class 'str'> b
<class 'int'> 125 <class 'str'> c
2, range(stop)
range(start, stop, step)
from collections.abc import Iterable, Iterator result = range(3) print(type(result)) # <class 'range'>, 每次返回一个整数 print(isinstance(result, Iterable)) # True print(isinstance(result, Iterator)) # False for item in result: print(type(item), item)
运行结果：
<class 'int'> 0
<class 'int'> 1
<class 'int'> 2
from collections.abc import Iterable, Iterator result = range(5, 3, -1) print(type(result)) # <class 'range'>, 每次返回一个整数 print(isinstance(result, Iterable)) # True print(isinstance(result, Iterator)) # False for item in result: print(type(item), item)
运行结果：
<class 'int'> 5
<class 'int'> 4
3, max
用于list
my_list = ["aa", "b", "c"] print(max(my_list)) # c print(max(my_list, key=lambda x: len(x))) # aa
用于dict
my_dict = {"aa":1, "b":2, "c":3}
print(max(my_dict)) # c
print(max(my_dict, key=lambda x:len(x))) # aa
用于tuple
my_tuple = ("aa", "b", "c") print(max(my_tuple)) # c print(max(my_tuple, key=lambda x:len(x))) # aa
4, len
用于list
my_list = ["aa", "b", "c"] print(len(my_list)) # 3
用于dict
my_dict = {"aa":1, "b":2, "c":3}
print(len(my_dict)) # 3
用于set
my_set = ("aa", "b", "c") print(len(my_set)) # 3
用于tuple
my_tuple = ("aa", "b", "c") print(len(my_tuple)) # 3
用于str
my_str = "ab" print(len(my_str)) # 2
参考
Python 中的枚举函数 enumerate() 详解 (baidu.com)
Python3 range() 函数用法 | 菜鸟教程 (runoob.com)