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python basics--list

高洛峰
高洛峰Original
2017-02-17 11:41:121236browse

List

List is one of the most commonly used data types. Lists can achieve the most convenient storage, modification and other operations on data

1. Define the list

fruits = ['apple','banana','orange']

2. Access elements in the list through subscripts, and the subscripts start counting from 0

>>> fruits[0]
'apple'
>>> fruits[2]
'orange'
>>> fruits[-1]
'orange'
>>> fruits[-2]
'banana'

3. Slicing

>>> fruits = ['apple','banana','orange','peal','grape']
>>> fruits[1:4]    #取下标1到下标4之间的数,包括1但不包括4
['banana', 'orange', 'peal']
>>> fruits[1:-1]   #取下标1至-1之间的数,不包括-1
['banana', 'orange', 'peal']
>>> fruits[0:3]    #从头开始取,不包括3
['apple', 'banana', 'orange']
>>> fruits[:3]     #和上句一样
['apple', 'banana', 'orange']
>>> fruits[3:]     #从下标3到最后,到末尾只能这样取
['peal', 'grape']
>>> fruits[0::2]   #从头开始,步长为2,即隔一个取一个
['apple', 'orange', 'grape']
>>> fruits[::2]    #和上句一iy
['apple', 'orange', 'grape']

4. Append, append()

>>> fruits
['apple', 'banana', 'orange', 'peal', 'grape']
>>> fruits.append('newpeach')
>>> fruits
['apple', 'banana', 'orange', 'peal', 'grape', 'newpeach']

5 .Insert element, insert()

Insert a watermelon at subscript 1

['apple', 'banana', 'orange', 'peal', 'grape', 'newpeach']
>>> fruits.insert(1,'watermelon')
>>> fruits
['apple', 'watermelon', 'banana', 'orange', 'peal', 'grape', 'newpeach']

6. Modify the elements in the list

Change banana to cherry

>>> fruits
['apple', 'watermelon', 'banana', 'orange', 'peal', 'grape', 'newpeach']
>>> fruits[2]='cherry'
>>> fruits
['apple', 'watermelon', 'cherry', 'orange', 'peal', 'grape', 'newpeach']

7. Delete

pop() will return the last element after deleting it by default

>>> fruits
['apple', 'watermelon', 'cherry', 'orange', 'peal', 'grape', 'newpeach']
>>> del fruits[2]    #删除第二个元素
>>> fruits
['apple', 'watermelon', 'orange', 'peal', 'grape', 'newpeach']
>>> fruits.remove('orange')     #删除指定的元素
>>> fruits
['apple', 'watermelon', 'peal', 'grape', 'newpeach']
>>> fruits.pop()    #删除最后一个元素
'newpeach'
>>> fruits
['apple', 'watermelon', 'peal', 'grape']

8. Extend extend()

 >>> fruits
['apple', 'watermelon', 'peal', 'grape']
>>> vegetable = ['radish','cabbage','cucumber']
>>> fruits
['apple', 'watermelon', 'peal', 'grape']
>>> vegetable
['radish', 'cabbage', 'cucumber']
>>> fruits.extend(vegetable)
>>> fruits
['apple', 'watermelon', 'peal', 'grape', 'radish', 'cabbage', 'cucumber']

9. Copy copy()

['apple', 'watermelon', 'peal', 'grape', 'radish', 'cabbage', 'cucumber']
>>> fruits2 = fruits.copy()
>>> fruits2
['apple', 'watermelon', 'peal', 'grape', 'radish', 'cabbage', 'cucumber']

10. Statistics count()

 >>> fruits.count('apple')
 1

11. Sort sort() and flip reverse()

>>> fruits
['apple', 'watermelon', 'peal', 'grape', 'radish', 'cabbage', 'cucumber']
>>> fruits.sort()
>>> fruits
['apple', 'cabbage', 'cucumber', 'grape', 'peal', 'radish', 'watermelon']
>>> fruits.reverse()
>>> fruits
['watermelon', 'radish', 'peal', 'grape', 'cucumber', 'cabbage', 'apple']

12. Get the subscript index ()

['watermelon', 'radish', 'peal', 'grape', 'cucumber', 'cabbage', 'apple']
>>> fruits.index('apple')
6
# 只返回找到的第一个下标


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