Python元组剖析

JSON 2024-04-03 16:04:48 248

什么是元组

元组是一个容器，它在括号之间保存一系列逗号分隔的值（项目或元素），例如 (x, y) 坐标。元组类似于列表，但它们是不可变的（即一旦创建就无法更改其内容）并且可以保存混合数据类型。元组在 Python 中扮演着一种“结构”的角色——一种传递一些逻辑的、固定大小的值包的便捷方法。

元组：命令

元组是一个不可变且可哈希的列表。

<tuple> = ()
<tuple> = (<el>, )
<tuple> = (<el_1>, <el_2> [, ...])

命名元组

Tuple 的子类具有命名元素。

>>> from collections import namedtuple
>>> Point = namedtuple('Point', 'x y')
>>> p = Point(1, y=2)
Point(x=1, y=2)
>>> p[0]
1
>>> p.x
1
>>> getattr(p, 'y')
2
>>> p._fields  # Or: Point._fields
('x', 'y')

创建一个元组？

要创建元组，只需列出括号内的值并用逗号分隔。 “空”元组只是一对空括号

>>> #create an empty tuple
>>> tuplex = ()
>>> print (tuplex)
()
>>> #create a tuple with different data types
>>> tuplex = ('tuple', False, 3.2, 1)
>>> print (tuplex)
('tuple', False, 3.2, 1)
>>> #create a tuple with numbers, notation without parenthesis
>>> tuplex = 4, 7, 3, 8, 1 
>>> print (tuplex)
(4, 7, 3, 8, 1)
>>> #create a tuple of one item, notation without parenthesis
>>> tuplex = 4, 
>>> print (tuplex)
(4,)
>>> #create an empty tuple with tuple() function built-in Python
>>> tuplex = tuple()
>>> print (tuplex)
()
>>> #create a tuple from a iterable object
>>> tuplex = tuple([True, False]) 
>>> print (tuplex)
(True, False)
>>>

如何在Python中获取元组的一项？

>>> #create a tuple
>>> tuplex = ("w", 3, "r", "e", "s", "o", "u", "r", "c", "e") 
>>> print(tuplex)
('w', 3, 'r', 'e', 's', 'o', 'u', 'r', 'c', 'e')
>>> #get item (4th element)of the tuple by index
>>> item = tuplex[3]
>>> print(item)
e
>>> #get item (4th element from last)by index negative
>>> item1 = tuplex[-4]
>>> print(item1)
u
>>>

如何知道Python中的元组中是否存在某个元素？

>>> #create a tuple
>>> tuplex = ("w", 3, "r", "e", "s", "o", "u", "r", "c", "e")
>>> print(tuplex)
('w', 3, 'r', 'e', 's', 'o', 'u', 'r', 'c', 'e')
>>> #use in statement
>>> print("r" in tuplex)
True
>>> print(5 in tuplex)
False
>>>

列表到元组

>>> #create list
>>> listx = [5, 10, 7, 4, 15, 3]
>>> print(listx)
[5, 10, 7, 4, 15, 3]
>>> #use the tuple() function built-in Python, passing as parameter the list
>>> tuplex = tuple(listx)
>>> print(tuplex)
(5, 10, 7, 4, 15, 3)
>>>

将元组解包为多个变量

>>> #create a tuple
>>> tuplex = 4, 8, 3 
>>> print(tuplex)
(4, 8, 3)
>>> n1, n2, n3 = tuplex
>>> #unpack a tuple in variables
>>> print(n1 + n2 + n3) 
15
>>> #the number of variables must be equal to the number of items of the tuple
>>> n1, n2, n3, n4 = tuplex 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 3 values to unpack
>>>

在Python元组中添加项目！

>>> #create a tuple
>>> tuplex = (4, 6, 2, 8, 3, 1) 
>>> print(tuplex)
(4, 6, 2, 8, 3, 1)
>>> #tuples are immutable, so you can not add new elements
>>> #using merge of tuples with the + operator you can add an element and it will create a new tuple
>>> tuplex = tuplex + (9,)
>>> print(tuplex)
(4, 6, 2, 8, 3, 1, 9)
>>> #adding items in a specific index
>>> tuplex = tuplex[:5] + (15, 20, 25) + tuplex[:5]
>>> print(tuplex)
(4, 6, 2, 8, 3, 15, 20, 25, 4, 6, 2, 8, 3)
>>> #converting the tuple to list
>>> listx = list(tuplex) 
>>> #use different ways to add items in list
>>> listx.append(30)
>>> tuplex = tuple(listx)
>>> print(tuplex)
(4, 6, 2, 8, 3, 15, 20, 25, 4, 6, 2, 8, 3, 30)
>>>

克隆一个元组

>>> from copy import deepcopy
>>> #create a tuple
>>> tuplex = ("HELLO", 5, [], True) 
>>> print(tuplex)
('HELLO', 5, [], True)
>>> #make a copy of a tuple using deepcopy() function
>>> tuplex_clone = deepcopy(tuplex)
>>> tuplex_clone[2].append(50)
>>> print(tuplex_clone)
('HELLO', 5, [50], True)
>>> print(tuplex)
('HELLO', 5, [], True)
>>>

在Python中如何知道一个项目重复的次数

>>> #create a tuple
>>> tuplex = 2, 4, 5, 6, 2, 3, 4, 4, 7 
>>> print(tuplex)
(2, 4, 5, 6, 2, 3, 4, 4, 7)
>>> #return the number of times it appears in the tuple.
>>> count = tuplex.count(4)
>>> print(count)
3
>>> count = tuplex.count(7)
>>> print(count)
1
>>> count = tuplex.count(5)
>>> print (count)
1
>>>

从元组中删除一个项目

>>> #create a tuple
>>> tuplex = "w", 3, "d", "r", "e", "s", "l" 
>>> print(tuplex)
('w', 3, 'd', 'r', 'e', 's', 'l')
>>> #tuples are immutable, so you can not remove elements
>>> #using merge of tuples with the + operator you can remove an item and it will create a new tuple
>>> tuplex = tuplex[:2] + tuplex[3:]
>>> print(tuplex)
('w', 3, 'r', 'e', 's', 'l')
>>> #converting the tuple to list
>>> listx = list(tuplex) 
>>> #use different ways to remove an item of the list
>>> listx.remove("l") 
>>> #converting the tuple to list
>>> tuplex = tuple(listx) 
>>> print(tuplex)
('w', 3, 'r', 'e', 's')
>>>

对元组进行切片

>>> #create a tuple
>>> tuplex = (2, 4, 3, 5, 4, 6, 7, 8, 6, 1) 
>>> #used tuple[start:stop] the start index is inclusive and the stop index
>>> _slice = tuplex[3:5] 
#is exclusive.
>>> print(_slice)
(5, 4)
>>> #if the start index isn't defined, is taken from the beg inning of the tuple.
>>> _slice = tuplex[:6]
>>> print(_slice)
(2, 4, 3, 5, 4, 6)
>>> #if the end index isn't defined, is taken until the end of the tuple
>>> _slice = tuplex[5:] 
>>> print(_slice)
(6, 7, 8, 6, 1)
>>> #if neither is defined, returns the full tuple
>>> _slice = tuplex[:]
>>> print(_slice)
(2, 4, 3, 5, 4, 6, 7, 8, 6, 1)
>>> #The indexes can be defined with negative values
>>> _slice = tuplex[-8:-4] 
>>> print(_slice)
(3, 5, 4, 6)
>>>

查找元组中某一项的索引

>>> #create a tuple
>>> tuplex = tuple("index tuple") 
>>> print(tuplex)
('i', 'n', 'd', 'e', 'x', ' ', 't', 'u', 'p', 'l', 'e')
>>> #get index of the first item whose value is passed as parameter
>>> index = tuplex.index("p") 
>>> print(index)
8
>>> #define the index from which you want to search
>>> index = tuplex.index("p", 5) 
>>> print(index)
8
>>> #define the segment of the tuple to be searched
>>> index = tuplex.index("e", 3, 6) 
>>> print(index)
3
>>> #if item not exists in the tuple return ValueError Exception
>>> index = tuplex.index("y")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: tuple.index(x): x not in tuple
>>>

元组的大小

>>> tuplex = tuple("w3resource")	#create a tuple
>>> print(tuplex)
('w', '3', 'r', 'e', 's', 'o', 'u', 'r', 'c', 'e')
>>> #use the len() function to known the length of tuple.
>>> print(len(tuplex))
10
>>>

如何在 Python 元组中使用运算符 + 和 *？

>>> #create a tuple
>>> tuplex = 5, #create a tuple
>>> #The * operator allow repeat the items in the tuple
>>> print(tuplex * 6) 
(5, 5, 5, 5, 5, 5)
>>> #create a tuple with repeated items.
>>> tuplex = (5, 10, 15) * 4 
>>> print(tuplex)
(5, 10, 15, 5, 10, 15, 5, 10, 15, 5, 10, 15)
>>> #create three tuples
>>> tuplex1 = (3, 6, 9, 12, 15) 
>>> tuplex2 = ("w", 3, "r", "s", "o", "u", "r", "c", "e")
>>> tuplex3 = (True, False)
>>> #The + operator allow create a tuple joining two or more tuples
>>> tuplex = tuplex1 + tuplex2 + tuplex3
>>> print(tuplex)
(3, 6, 9, 12, 15, 'w', 3, 'r', 's', 'o', 'u', 'r', 'c', 'e', True, False)
>>>

使用步骤参数的元组切片

>>> #create a tuple
>>> tuplex = tuple("HELLO WORLD") 
>>> print(tuplex)
('H', 'E', 'L', 'L', 'O', ' ', 'W', 'O', 'R', 'L', 'D')
>>> #step specify an increment between the elements to cut of the tuple.
>>> _slice = tuplex[2:9:2]	#tuple[start:stop:step]
>>> print(_slice)
('L', 'O', 'W', 'R')
>>> #returns a tuple with a jump every 3 items.
>>> _slice = tuplex[::4] 
>>> print(_slice)
('H', 'O', 'R')
>>> #when step is negative the jump is made back
>>> _slice = tuplex[9:2:-4] 
>>> print(_slice)
('L', ' ')
>>> #when step is negative the jump is made back
>>> _slice = tuplex[9:2:-3]	 
>>> print(_slice)
('L', 'W', 'L')
>>>

修改元组的项目

>>> #create a tuple
>>> tuplex = ("w", 3, "r", [], False)
>>> print(tuplex)
('w', 3, 'r', [], False)
>>> #tuples are immutable, so you can not modify items which are also immutable, as str, boolean, numbers etc.
>>> tuplex[3].append(200)
>>> print(tuplex)
('w', 3, 'r', [200], False)
>>>