Python Basics Four

List: Python one of the underlying data types

Other languages also have a list of concepts,js--> arrays, indexable, can be sliced, can be added in step

A list can store a large amount of data 32-bit Python is limited to 536,870,912 elements, and 64-bit Python is limited to 1.,152,921,504,606,85e,+18 elements.

li = [1, 'txt', {'name': 'python', 'author':'龟叔'}, [2, 3, 4], (5, 6)]

First: Index, slice, slice + step.

>>> li[2]{'name': 'python', 'author': '龟叔'}>>> li[2:][{'name': 'python', 'author': '龟叔'}, [2, 3, 4], (5, 6)]>>> li[-2::-1][[2, 3, 4], {'name': 'python', 'author': '龟叔'}, 'txt', 1]

Second: Adding and deleting changes

li2 = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']

Add Append end Append

>>> li2.append('13')>>> li2['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec', '13']

Insert Insertion

>>> li2.insert(6, 'Jul')>>> li2['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec', '13']

Extend iterative Append

>>> li2.extend('abc')>>> li2['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec', '13', 'a', 'b', 'c']>>> li2.extend(['aa', 'bb'])>>> li2['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec', '13', 'a', 'b', 'c', 'aa', 'bb']

Delete Pop by index to delete, return the deleted element

li3 = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']>>> li3 = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']>>> li3.pop(0)'Jan'>>> li3['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']

Remove succeeds without a return value by element deletion, unsuccessful error

li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3.remove('Feb')>>> li3['Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3.remove('Feb')Traceback (most recent call last):  File "<stdin>", line 1, in <module>ValueError: list.remove(x): x not in list

Clear clears the original variable to an empty array

>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3.clear()>>> li3[]

Del by index, slice, and can delete entire array in memory

>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> del li3[0]>>> li3['Mar', 'Apr', 'May', 'Jun', 'Jul']>>> del li3[-2:]>>> li3['Mar', 'Apr', 'May']>>> del li3>>> li3Traceback (most recent call last):  File "<stdin>", line 1, in <module>NameError: name 'li3' is not defined

Change by index

>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3[0] = 'February'>>> li3['February', 'Mar', 'Apr', 'May', 'Jun', 'Jul']

By slicing: The original array may be expanded or may be scaled down

>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3[:2] = [1, 2, 3, 4]>>> li3[1, 2, 3, 4, 'Apr', 'May', 'Jun', 'Jul']>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3[1:4] = [1, 2]>>> li3['Feb', 1, 2, 'Jun', 'Jul']

According to Slice + step: Only one by one corresponds

>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3[1:4] = [1, 2]>>> li3['Feb', 1, 2, 'Jun', 'Jul']

Check: index, slice, slice + step for loop

>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> for i in li3:...     print(i)...FebMarAprMayJunJul

Other methods

# len>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> len(li3)6# count>>> li3.count('Feb')1# index 如同str一样：没有会报错>>> li3.index('bad')Traceback (most recent call last):  File "<stdin>", line 1, in <module>ValueError: 'bad' is not in list>>> li3.index('Mar')1# sort()-->从小到大，当有reverse=True时-->从大到小>>> li3 = ['Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul']>>> li3.sort()>>> li3['Apr', 'Feb', 'Jul', 'Jun', 'Mar', 'May']>>> li3.sort(reverse=True)>>> li3['May', 'Mar', 'Jun', 'Jul', 'Feb', 'Apr']

Python Basics Four