[Python] How to use list 3 Added

Introduction

We are advancing Python learning according to Learning Roadmap for Python Beginners on Tommy's blog. This time, I will deal with the latter half of [Introduction to Python] Summary of how to use list (Part 1).

Target person

--Those who are studying on Tomi-san's blog --For those who want to get an overview of how to use list

environment

Google Colaboratory

content of study

Use ** Add Method ** to add data to the list

Additional methods

1. append
2. extend
3. insert

Because these are methods

List variable.append()

 I use it.

list_a = [1, 2, 3, 4] #1,2,3,4 list_a list_a.append(5) #list_Add 5 to A at the end print(list_a)

#### **`Execution result`**
```text

[1, 2, 3, 4, 5]         #5 was added last.

Next, let's add the lists together

list_a = [1,2,3,4]
list_b = [5,6]
list_a.append(list_b)
print(list_a)

Execution result

[1, 2, 3, 4, [5, 6]]    #Since append is added as it is[]Will also be added

[] When you don't want to match

list_a = [1,2,3,4]
list_b = [5,6]
list_a.extend(list_b)    #Let's use extend
print(list_a)

Execution result

[1, 2, 3, 4, 5, 6]       #Only the numbers were matched!!

Since extend is a combination of lists, let's create a list

Cannot be used like append

list_a = [1,2,3,4]
list_a.extend(5)

Execution result

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-9-25c1d760cd29> in <module>()
      1 #Note: Since extend is a combination of lists, create a list and use it.
      2 list_a = [1,2,3,4]
----> 3 list_a.extend(5)

TypeError: 'int' object is not iterable

Will result in an error

insert can be added to the element No in list !!

list_a = [1, 2, 3, 4]
list_b = [5, 6]
list_a.insert(1, list_b)    #Element No.List to 1_b[5, 6]Add
print(list_a)

Execution result

[1, [5, 6], 2, 3, 4]        #Added and printed

insert mystery

list_a = [1, 2, 3, 4]
list_b = [5]

list_a.insert(0, list_b)
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(1, list_b)
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(2, list_b)
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(3, list_b)
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(4, list_b)
print(list_a)

Execution result

[[5], 1, 2, 3, 4]    #Element No. 0
[1, [5], 2, 3, 4]    #Element No. 1
[1, 2, [5], 3, 4]    #Element No. 2
[1, 2, 3, [5], 4]    #Element No. 3
[1, 2, 3, 4, [5]]    #Element No. 4

This is OK. Then what is this?

list_a = [1, 2, 3, 4]
list_b = [5]

list_a.insert(-4, list_b)    #Element No. -4
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(-3, list_b)    #Element No. -3
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(-2, list_b)    #Element No. -2
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(-1, list_b)    #Element No. -1
print(list_a)

list_a = [1, 2, 3, 4]
list_a.insert(0, list_b)     #Element No. 0
print(list_a)

Execution result

[[5], 1, 2, 3, 4]    #Element No. -4
[1, [5], 2, 3, 4]    #Element No. -3
[1, 2, [5], 3, 4]    #Element No. -2
[1, 2, 3, [5], 4]    #Element No. -1 Doesn't it come to the end of the element? that?
[[5], 1, 2, 3, 4]    #Element No. 0

I'm not sure right now ...

Next time, I plan to delete clear, pop, remove, del.

reference

[Introduction to Python] Summary of how to use list (Part 1)