Python:在列表中修改添加和删除元素

Posted 2021-02-20 pyme

一、修改

代码示例

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘] 
print(motorcycles) 

motorcycles[0] = ‘ducati‘ 
print(motorcycles)

运行结果

[‘honda‘, ‘yamaha‘, ‘suzuki‘] 
[‘ducati‘, ‘yamaha‘, ‘suzuki‘]

二、添加

　　（一）使用append()添加在末尾

代码示例

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘] 
print(motorcycles) 

motorcycles.append(‘ducati‘) 
print(motorcycles) 

方法append()将元素‘ducati‘添加到了列表末尾，而不影响列表中的其他所有元素：

[‘honda‘, ‘yamaha‘, ‘suzuki‘] 
[‘honda‘, ‘yamaha‘, ‘suzuki‘, ‘ducati‘]

　　（二）使用insert()在列表任意位置插入元素（需要指定新元素的索引和值）

代码示例

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘] 
motorcycles.insert(0, ‘ducati‘) 
print(motorcycles)

运行结果

[‘ducati‘, ‘honda‘, ‘yamaha‘, ‘suzuki‘]

三、删除

　　（一）使用del语句删除元素（知道要删除的元素在列表中的位置）

代码示例

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘] 
print(motorcycles) 

del motorcycles[0] 
print(motorcycles)

运行结果

[‘honda‘, ‘yamaha‘, ‘suzuki‘] 
[‘yamaha‘, ‘suzuki‘]

　　（二）使用方法pop()删除元素（要将元素从列表中删除，并接着使用它的值，可以使用pop()来删除列表中任何位置的元素，只需在括号中指定要删除的元素的索引即可。）

代码示例①

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘] 
print(motorcycles) 
popped_motorcycle = motorcycles.pop() 
print(motorcycles) 
print(popped_motorcycle)

运行结果①（.pop()删除了列表中的末尾元素）

[‘honda‘, ‘yamaha‘, ‘suzuki‘] 
[‘honda‘, ‘yamaha‘] 
suzuki

代码示例②

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘] 
first_owned = motorcycles.pop(0) 
print(‘The first motorcycle I owned was a ‘ + first_owned.title() + ‘.‘)

运行结果②

The first motorcycle I owned was a Honda.

　　（三）根据值删除元素（只知道要删除的元素的值，不知道要从列表中删除的值所处的位置。可使用方法remove()，可接着使用它的值）

代码示例①

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘, ‘ducati‘] 
print(motorcycles) 
motorcycles.remove(‘ducati‘) 
print(motorcycles)

运行结果①

[‘honda‘, ‘yamaha‘, ‘suzuki‘, ‘ducati‘] 
[‘honda‘, ‘yamaha‘, ‘suzuki‘]

代码示例②

motorcycles = [‘honda‘, ‘yamaha‘, ‘suzuki‘, ‘ducati‘]
print(motorcycles) 
too_expensive = ‘ducati‘ 
motorcycles.remove(too_expensive) 
print(motorcycles) 
print("
A " + too_expensive.title() + " is too expensive for me.")

运行结果②

[‘honda‘, ‘yamaha‘, ‘suzuki‘, ‘ducati‘] 
[‘honda‘, ‘yamaha‘, ‘suzuki‘] 
A Ducati is too expensive for me.