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python list append multiple times

How to python list append multiple times

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In this article we will saw How to add similar value in multiple times in python list so let’s see:

3 methods for python list append multiple times

Basically we are use three methods for python

  1. Using * operator
  2. Using extend()+ list comprehension
  3. Using extend() + itertools.repeat()
python list append multiple times
python list append multiple times
 

Method 01) Python append list multiple times using * operator

For Different data types:
list = [0] * 20
[0, 0, 0, 0, 0, …] It's get result all zeros up to 20 times
Similarly
list = ['pythonslearning'] * 100
['pythonslearning', 'pythonslearning', 'pythonslearning', 'pythonslearning', …]

Method 02) python append list multiple time using list.extend()


list = [{} for x in range(20)]
In the above method the second one is best method for constant values, like as int or string. but why? the answer is when we use the syntax like only a shallow copy is does and if we use something like as syntax [{}]100 then it end up with 100 references to the same dictionary and hence change one of them would change them all. and the result is int and string are immutable.
You can use the extend() methods of that list If you want to add to an existing lists.
Method #01) list.extend()
Method #02) generator expression:

l.extend(generate_value() for _ in range(n))

This will add a value n times. Note that this will evaluate generate_value() each time, side-stepping issues with mutable values that other answers may have

[[5]] * 4
[[5], [5], [5], [5]

_[0].append(1)

[[5, 5], [5, 5], [5, 5], [5, 5], [5, 5]]

_

[[5] for _ in range(5)]

[[5], [5], [5], [5], [5]]

[[5, 5], [5], [5], [5], [5]]

_[0].append(1)

_
When using the First method like multiplication method,we end up with a lists of n reference to the same lists.
When using second method like a generator expressions or lists comprehension,for this method a new lists is created for each sub-item, so each item is a different value in every time.

Some FAQ about python list append multiple times

01)What is the difference between append and extend in Python?
Append:
Argument is a single elements to the end of a lists append adds its and length of the lists itself will increase by one.
Extend:
Extend is a arguments adding to each elements to the lists and extending the list and length of the lists increase by many position.

02) How do I store multiple values in a list Python?
There are many ways to store multiple values in list python:

1 We use the append() methods for this append() function
2 we use the insert() methods for the insert() values in a list.
3 we use the extend() methods they add multiple items to a list.

Summary:
In this article we covered different topic like How to append an item to a list in multiple times, difference between append and extend in Python,store multiple values in a list Python. about this section if you have any query then comment.
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I am Mr. Sachin pagar Embedded system engineer, the founder of Pythonslearning, a Passionate Educational Blogger and Author, who love to share the informative content on educational resources.

sachin Pagar

I am Mr. Sachin pagar Embedded system engineer, the founder of Pythonslearning, a Passionate Educational Blogger and Author, who love to share the informative content on educational resources.

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