Deleting elements in python list is mainly divided into the following 3 scenarios:
- Delete according to the index position of the target element, you can use the del keyword or pop() method;
- Delete according to the value of the element itself, and use the remove() method provided by the list (list type);
- To delete all elements in the list, you can use the clear() method provided by the list (list type);
del: Delete elements based on index value
del is a keyword in python, specially used to perform deletion operations. It can not only delete the entire list, but also delete certain elements in the list.
del can delete individual elements in a list in the format:
- del listname[index]
listname: indicates the list name
index: represents the index value
list = ["python",1,2,"java"]
print(list)
#Use positive index
del list[2]
print(list)
#Use negative index
del list[-1]
print(list)['python', 1, 2, 'java']
['python', 1, 'java']
['python', 1]
del can delete a continuous element in the middle, in the format:
- del listname[start,end]
start: Start index
end: end index
list = ["python",1,2,"java"]
print(list)
#Use positive index
del list[2:3]
print(list)
list = ["python",1,2,"java"]
print(list)
#Use negative index
del list[-3:-1]
print(list)['python', 1, 2, 'java']
['python', 1, 'java']
['python', 1, 2, 'java']
['python', 'java']
del will delete elements from the start index to the end index, excluding elements at the end position
pop(): Delete elements based on index value
This method is used to delete elements at the specified index in the list
Syntax: (index)
listname: indicates the list name
index: represents the index value
list = ["python",1,2,"java",78,9,80,90]
print(list)
(3)
print(list)['python', 1, 2, 'java', 78, 9, 80, 90]
['python', 1, 2, 78, 9, 80, 90]
If the index parameter is not written, the last element in the list will be deleted by default, similar to the "stack" operation in the data structure
list = ["python",1,2,"java",78,9,80,90]
print(list)
()
print(list)['python', 1, 2, 'java', 78, 9, 80, 90]
['python', 1, 2, 'java', 78, 9, 80]
remove(): Delete according to element value
This method will delete the element itself based on the value of the element itself
list = ["python",1,2,"java",78,9,80,90,2,34,2]
print(list)
#First delete 2
(2)
print(list)
#First delete 2
(2)
print(list)
#First delete 2
(2)
print(list)['python', 1, 2, 'java', 78, 9, 80, 90, 2, 34, 2]
['python', 1, 'java', 78, 9, 80, 90, 2, 34, 2]
['python', 1, 'java', 78, 9, 80, 90, 34, 2]
['python', 1, 'java', 78, 9, 80, 90, 34]
Note: The remove() method will only delete the first element with the same value as the specified value, and it must be guaranteed that the element exists, otherwise a ValueError error will be raised. Therefore, it is best to make a judgment in advance when we use remove() to delete the element.
clear(): Delete all elements
clear() is used to delete all elements of the list, that is, to clear the list
grammar:()
listname: indicates the list name
list = ["python",1,2,"java",78,9,80,90,2,34,2]
print(list)
()
print(list)
['python', 1, 2, 'java', 78, 9, 80, 90, 2, 34, 2]
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