How to Add elements to a List in a Loop in Python

# Table of Contents

1. Add elements to a List in a Loop in Python
2. Add multiple elements to a list in a for loop
3. Add items to a List while iterating over it in Python
4. Add all elements of an iterable to a List in Python

# Add elements to a List in a Loop in Python

To add elements to a list in a loop:

1. Use the range() class to get a range object you can iterate over.
2. Use a for loop to iterate over the range object.
3. Use the list.append() method to add elements to the list.

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my_list = ['bobby', 'hadz', 'com']

for i in range(3):
    my_list.append('new')

# 👇️ ['bobby', 'hadz', 'com', 'new', 'new', 'new']
print(my_list)

We used the range() class to get a range object.

The range class is commonly used for looping a specific number of times in for loops and takes the following arguments:

If you only pass a single argument to the range() constructor, it is considered to be the value for the stop parameter.

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my_list = ['bobby', 'hadz', 'com']

print(list(range(len(my_list))))  # 👉️ [0, 1, 2]
print(list(range(4)))  # 👉️ [0, 1, 2, 3]
print(list(range(5)))  # 👉️ [0, 1, 2, 3]

Copied!
my_list = ['bobby', 'hadz', 'com']

for i in range(len(my_list)):
    my_list.append('new')

# 👇️ ['bobby', 'hadz', 'com', 'new', 'new', 'new']
print(my_list)

The list.append() method adds an item to the end of the list.

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my_list = ['bobby', 'hadz']

my_list.append('com')

print(my_list)  # 👉️ ['bobby', 'hadz', 'com']

The method returns None as it mutates the original list.

# Add multiple elements to a list in a for loop

If you need to add multiple elements to a list in a for loop, use the list.extend() method.

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my_list = ['bobby', 'hadz', 'com']

for i in range(2):
    my_list.extend(['1', '2'])

# 👇️ ['bobby', 'hadz', 'com', '1', '2', '1', '2']
print(my_list)

The list.extend() method takes an iterable (such as a list) and extends the list by appending all of the items from the iterable.

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my_list = ['bobby']

my_list.extend(['hadz', '.', 'com'])

print(my_list)  # 👉️ ['bobby', 'hadz', '.', 'com']

The list.extend method returns None as it mutates the original list.

# Add items to a List while iterating over it in Python

To add items to a list while iterating over it:

1. Use the range() class to create a range object according to the list's length.
2. Iterate over the range object.
3. Use the list.append() method to add items to the list while iterating.

Copied!
my_list = ['bobby', 'hadz', 'com']


for index in range(len(my_list)):
    my_list.append('another')

# 👇️ ['bobby', 'hadz', 'com', 'another', 'another', 'another']
print(my_list)

The range() class is commonly used for looping a specific number of times in for loops and takes the following arguments:

If you only pass a single argument to the range() constructor, it is considered to be the value for the stop parameter.

Copied!
my_list = ['bobby', 'hadz', 'com']

print(list(range(len(my_list))))  # 👉️ [0, 1, 2]
print(list(range(3)))  # 👉️ [0, 1, 2]

The list.append() method adds an item to the end of the list.

Copied!
my_list = ['bobby', 'hadz', 'com']


for index in range(len(my_list)):
    my_list.append('another')

# 👇️ ['bobby', 'hadz', 'com', 'another', 'another', 'another']
print(my_list)

If you need to add multiple items to the list while iterating, use the list.extend() method.

Copied!
my_list = ['bobby', 'hadz', 'com']


for index in range(len(my_list)):
    my_list.extend(['one', 'two'])

# 👇️ ['bobby', 'hadz', 'com', 'one', 'two', 'one', 'two', 'one', 'two']
print(my_list)

The list.extend method takes an iterable (such as a list) and extends the list by appending all of the items from the iterable.

Copied!
my_list = ['bobby']

my_list.extend(['hadz', '.', 'com'])

print(my_list)  # 👉️ ['bobby', 'hadz', '.', 'com']

Alternatively, you can use the list.copy() method.

# Add items to a List while iterating over it using list.copy()

This is a two-step process:

1. Use a for loop to iterate over a copy of the list.
2. On each iteration, use the list.append() method to add an item to the list.

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my_list = ['bobby', 'hadz', 'com']

for item in my_list.copy():
    my_list.append('another')


# 👇️ ['bobby', 'hadz', 'com', 'another', 'another', 'another']
print(my_list)

We used the list.copy() method to get a copy of the list.

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my_list = ['bobby', 'hadz', 'com']

print(my_list.copy())  # 👉️ ['bobby', 'hadz', 'com']

The list.copy() method returns a shallow copy of the object on which the method was called.

However, we can iterate over a copy of the list and modify the contents of the original list.

# Add all elements of an iterable to a List in Python

Use the list.extend() method to add all elements of an iterable to a list.

The list.extend() method will append the elements of the iterable to the list.

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a_list = ['bobby']

iterable = ['hadz', '.', 'com']

a_list.extend(iterable)
print(a_list)  # 👉️ ['bobby', 'hadz', '.', 'com']

The list.extend() method takes an iterable and extends the list by appending all of the items from the iterable.

The list.extend method returns None as it mutates the original list.

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a_list = ['bobby']

a_list.extend(range(1, 5))
print(a_list)  # 👉️ ['bobby', 1, 2, 3, 4]

# Insert the elements of the iterable into the list at a specific index

If you need to insert the elements of the iterable into the list at a specific index, use list slicing.

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a_list = ['bobby', 'hadz']
iterable = ('.', 'com')

a_list[1:1] = iterable
print(a_list)  # 👉️ ['bobby', '.', 'com', 'hadz']

The syntax for list slicing is my_list[start:stop:step].

The start index is inclusive and the stop index is exclusive (up to, but not including).

The list slicing assignment inserts the elements of the iterable into the list at the specified index.

Alternatively, you can use a for loop.

# Add all elements of an iterable to a List using a for loop

This is a two-step process:

1. Use a for loop to iterate over the iterable.
2. Use the list.append() method to add each element of the iterable to the list.

Copied!
a_list = ['bobby']

iterable = ('hadz', '.', 'com')

for item in iterable:
    a_list.append(item)

print(a_list)  # 👉️ ['bobby', 'hadz', '.', 'com']

We used a for loop to iterate over the iterable.

On each iteration, we use the list.append() method to append the current element to the list.

The list.append() method adds an item to the end of the list.

Copied!
my_list = ['bobby', 'hadz']

my_list.append('com')

print(my_list)  # 👉️ ['bobby', 'hadz', 'com']

The method returns None as it mutates the original list.

Note that using the list.extend() method is more performant than calling list.append() for each element in the iterable.

I've also written an article on how to add items to a dictionary in a loop.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Detect the Last item in a List using a for loop in Python
• Remove elements from a List while iterating in Python
• Python: Find range overlap and Check if Ranges overlap
• RuntimeError: no running event loop in Python [Solved]
• Check if a List is Sorted (ascending/descending) in Python
• How to restart a Loop in Python