今天来梳理一下Python tuple类型的知识点，特此申明下面信息均参考自公司培训课PPT Nagiza F. Samatova, NC State Univ. All rights，主要涉及到下面几个点：
- • Immutable sequence of objects
- • Items: heterogeneous type and non-unique
- • Named tuples
- • Tuple operations
immutable: Content cannot be changed by adding, deleting, and altering items
new_tup = (3, 5, 2, 8)
new_tup[0] = 1
# output:
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-515-0b043ae6152f> in <module>
1 new_tup = (3, 5, 2, 8)
----> 2 new_tup[0] = 1
TypeError: 'tuple' object does not support item assignment
但是tuple可以包含mutable的元素，而且可以修改mutable元素的value
list_tuple = ([8, 7, 5], [1.8, 7.6, 3.5])
dics_tuple = ({
'name':'Lu', 'age':24}, {
'car':'BMW', 'y':2015})
print('original list_tuple:\n {}'.format(list_tuple))
print('original dics_tuple:\n {}'.format(dics_tuple))
list_tuple[0][1] = 1
dics_tuple[0]['age'] = 30
print('list_tuple after chang:\n {}'.format(list_tuple))
print('dics_tuple after change:\n {}'.format(dics_tuple))
# output:
original list_tuple:
([8, 7, 5], [1.8, 7.6, 3.5])
original dics_tuple:
({
'name': 'Lu', 'age': 24}, {
'car': 'BMW', 'y': 2015})
list_tuple after chang:
([8, 1, 5], [1.8, 7.6, 3.5])
dics_tuple after change:
({
'name': 'Lu', 'age': 30}, {
'car': 'BMW', 'y': 2015})
Named Tuples
● Use names instead of numerical indices to access items
用名字取代index访问tuple
● Created by using the namedtuple()factory function. The arguments are the name of the new class and a string containing the names of the elements
用到namedtuple() factory function
namedtuple(‘class name’, ‘the attibute of the class’)
from collections import namedtuple
Pet = namedtuple('Pet', 'kind name age')
dog = Pet(kind='dog', name='Tom', age=2)
cat = Pet(kind='cat', name='Snow', age=3)
print ('dog pet:\nkind:{}\tname:{}\tage:{}'.format(dog.kind, dog.name, dog.age))
print ('cat pet:\nkind:{}\tname:{}\tage:{}'.format(cat.kind, cat.name, cat.age))
# output:
dog pet:
kind:dog name:Tom age:2
cat pet:
kind:cat name:Snow age:3
Tuples: Operations
| Operation | Description | Result |
|---|---|---|
| len() | Length of the tuple | len(tup_1) |
| Concatenation(+) | Concatenate two tuples into a third one | tup_1 + tup_2 |
| Membership check (in) | Return True if item is in the tuple | 8 in tup_1 |
tup_1 = (5, 8, 9)
tup_2 = (4, 3)
print (len(tup_1))
print (tup_1 + tup_2)
print (8 in tup_1)
print (tup_2 * 3)
# output:
3
(5, 8, 9, 4, 3)
True
(4, 3, 4, 3, 4, 3)
Tuple: access and slice
nums = (0, 1, 2, 3, 4, 5, 6, 7)
print(nums[4])
print(nums[-5])
print(nums[:3])
print(nums[-6:-3])
print(nums[7:1:-2])
# output:
4
3
(0, 1, 2)
(2, 3, 4)
(7，5，3）
Create tuple object
empty tuple:
t = ()
t = tuple()
tuple(another_object)–有些python版本可能不支持
t1 = ('a',)
list_obj=[1,2,3,4,5,6]
t2 = tuple(list_obj)
t3 = 'a', 2, ['one', 'two']
t4 = tuple()
t4 = t4 + tuple('one')
print(t1)
print(t2)
print(t3)
print(t4)
# output:
('a',)
(1, 2, 3, 4, 5, 6)
('a', 2, ['one', 'two'])
('o', 'n', 'e')
count(value)
Returns the number of occurrences of an element in a tuple
t = (2,1,2,3,4,2)
print(t.count(2)) #output: 3
index(value)
Searches for the given element in a tuple and returns its position.
第一次出现的位置
t = (2,1,2,3,4,2)
print(t.index(2)) #output 0