0. definition:

A list is made up of columns of elements arranged in a specific order.

You can add anything to the list, and there can be no relationship between the elements;

Example:

demo_list = [1,"python",[0,1,2],{'URL':'https://blog.csdn.net/'}]

 

1. index

The first element of the list starts at 0, not 1;

Negative index, which allows the list to look up elements in reverse order.

list[0]: is the first element of the list

list[-2]: is the last element of the list

 

2. Modify, add and delete

Amendment:

a = [0,1,2,3,4,5,6,7,8,9]
a[5] = "five"
print(a)
#result:[0, 1, 2, 3, 4, 'five', 6, 7, 8, 9]

Add to:

• Add at the end of the list, using list.append()

a = [0,1,2,3,4,5,6,7,8,9]
a.append(10)
print(a)
#result:[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

• Add in the middle of the list, using list.insert()

a = [0,1,2,3,4,5,6,7,8,9]
a.insert(5,10)
print(a)
#result:[0, 1, 2, 3, 4, 10, 5, 6, 7, 8, 9]

The following method is also feasible, but not commonly used:

a = [0,1,2,3,4,5,6,7,8,9]
a[5:6] = [5,2018,2019,2020,2021]
print(a)
#result:[0, 1, 2, 3, 4, 5, 2018, 2019, 2020, 2021, 6, 7, 8, 9]

Delete:

• Delete with del

a = [0,1,2,3,4,5,6,7,8,9]
del a[5]
print(a)
#result:[0, 1, 2, 3, 4, 6, 7, 8, 9]

• Pop up delete using pop()

a = [0,1,2,3,4,5,6,7,8,9]
a.pop()
print(a)
#result:[0, 1, 2, 3, 4, 6, 7, 8]

• Pop anywhere element

a = [0,1,2,3,4,5,6,7,8,9]
a.pop(5)
print(a)
#result:[0, 1, 2, 3, 4, 6, 7, 8, 9]

• Delete based on element value

week = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']
week.remove('Monday')
print(week)
#result:['Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']

 

3. List sorting

• Permanent sorting

week = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']
week.sort()
print(week)
#result:['Friday', 'Monday', 'Saturday', 'Sunday', 'Thursday', 'Tuesday', 'Wednesday']

• Temporary sort

week = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']
print(sorted(week))
#result:['Friday', 'Monday', 'Saturday', 'Sunday', 'Thursday', 'Tuesday', 'Wednesday']
print(week)
#result:['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']

 

4. Reverse rotation

week = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']
week.reverse()
print(week)
#result:['Sunday', 'Saturday', 'Friday', 'Thursday', 'Wednesday', 'Tuesday', 'Monday']

Note: list.reverse() has no return value, so print(list.reverse()) and l = list.reverse() get None

The same is true for list.sort().

import numpy as np

a = np.arange(10).tolist()
b = a.reverse()
print(b)
#result:None

5. List length

week = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']
print(len(week))
#result:7

6.list.index()

Usage: l.index (value, [start, [stop]]) > integer -- return first index of value

Returns the index of the element value. You can specify the start and end of the search.

week = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday']
print(week.index('Tuesday',0,5))
#result:1

The start and end points can specify the search range:

import numpy as np

a = np.arange(10).tolist()
b = np.arange(10).tolist()
c = a + b
print(c)
#result:[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
print(1)
#result:1
print(c.index(1,5,15))
#result:11