Replace integer in list Python

In this tutorial, youll learn how to use Python to replace an item or items in a list. Youl learn how to replace an item at a particular index, how to replace a particular value, how to replace multiple values, and how to replace multiple values with multiple values.

Being able to work with lists is an important skill for any Python developer, given how prevalent and understandable these Python data structures are.

Lets get started with looking at what youll learn!

Table of Contents

  • Replace an Item in a Python List at a Particular Index
  • Replace a Particular Value in a List in Python Using a For Loop
  • Replace a Particular Value in a List in Python Using a List Comprehension
  • Change All Values in a List in Python Using a Function
  • Replace Multiple Values in a Python List
  • Replace Multiple Values with Multiple Values in a Python List
  • Conclusion

Replace an Item in a Python List at a Particular Index

Python lists are ordered, meaning that we can access (and modify) items when we know their index position. Python list indices start at 0 and go all the way to the length of the list minus 1.

You can also access items from their negative index. The negative index begins at -1 for the last item and goes from there. To learn more about Python list indexing, check out my in-depth overview here.

Replace integer in list Python
Replace integer in list Python

If we want to replace a list item at a particular index, we can simply directly assign new values to those indices.

Lets take a look at what that looks like:

# Replace an item at a particular index in a Python list a_list = [1, 2, 3, 4, 5, 6, 7, 8, 9] # Mofidy first item a_list[0] = 10 print(a_list) # Returns: [10, 2, 3, 4, 5, 6, 7, 8, 9] # Modify last item a_list[-1] = 99 print(a_list) # Returns: [10, 2, 3, 4, 5, 6, 7, 8, 99]

In the next section, youll learn how to replace a particular value in a Python list using a for loop.

Want to learn how to use the Python zip() function to iterate over two lists? This tutorial teaches you exactly what the zip() function does and shows you some creative ways to use the function.

Replace a Particular Value in a List in Python Using a For Loop

Python lists allow us to easily also modify particular values. One way that we can do this is by using a for loop.

One of the key attributes of Python lists is that they can contain duplicate values. Because of this, we can loop over each item in the list and check its value. If the value is one we want to replace, then we replace it.

Lets see what this looks like. In our list, the word apple is misspelled. We want to replace the misspelled version with the corrected version.

# Replace a particular item in a Python list a_list = ['aple', 'orange', 'aple', 'banana', 'grape', 'aple'] for i in range(len(a_list)): if a_list[i] == 'aple': a_list[i] = 'apple' print(a_list) # Returns: ['apple', 'orange', 'apple', 'banana', 'grape', 'apple']

Lets take a look at what weve done here:

  1. We loop over each index in the list
  2. If the index position of the list is equal to the item we want to replace, we re-assign its value

In the next section, youll learn how to turn this for loop into a Python list comprehension.

Want to learn more about Python for-loops? Check out my in-depth tutorial that takes your from beginner to advanced for-loops user! Want to watch a video instead? Check out my YouTube tutorial here.

Replace a Particular Value in a List in Python Using a List Comprehension

One of the key attributes of Python list comprehensions is that we can often turn for loops into much shorter comprehensions. Lets see how we can use a list comprehension in Python to replace an item in a list.

Well use the same example we used in the for loop, to help demonstrate how elegant a Python list comprehension can be:

# Replace a particular item in a Python list using a list comprehension a_list = ['aple', 'orange', 'aple', 'banana', 'grape', 'aple'] a_list = ['apple' if item == 'aple' else item for item in a_list] print(a_list) # Returns: ['apple', 'orange', 'apple', 'banana', 'grape', 'apple']

We can see here that there are two main benefits of list comprehensions compared to for loops:

  1. We dont need to initialize an empty list
  2. The comprehension reads in a relatively plain English

In the next section, youll learn how to change all values in a list using a formula.

Want to learn more about Python list comprehensions? Check out this in-depth tutorial that covers off everything you need to know, with hands-on examples. More of a visual learner, check out my YouTube tutorial here.

Change All Values in a List in Python Using a Function

Neither of the approaches above are immediately clear as to what they are doing. Because of this, developing a formula to do this is a helpful approach to help readers of your code understand what it is youre doing.

Lets take a look at how we can use the list comprehension approach and turn it into a formula:

# Replace a particular item in a Python list using a function a_list = ['aple', 'orange', 'aple', 'banana', 'grape', 'aple'] def replace_values(list_to_replace, item_to_replace, item_to_replace_with): return [item_to_replace_with if item == item_to_replace else item for item in list_to_replace] replaced_list = replace_values(a_list, 'aple', 'apple') print(replaced_list) # Returns: ['apple', 'orange', 'apple', 'banana', 'grape', 'apple']

Here, we simply need to pass in the list, the item we want to replace, and the item we want to replace it with. The function name makes it easy to understand what were doing, guiding our readers to better understand our actions.

In the next section, youll learn how to replace multiple values in a Python list.

Want to learn how to use the Python zip() function to iterate over two lists? This tutorial teaches you exactly what the zip() function does and shows you some creative ways to use the function.

Replace Multiple Values in a Python List

There may be many times when you want to replace not just a single item, but multiple items. This can be done quite simply using the for loop method shown earlier.

Lets take a look at an example where we want to replace all known typos in a list with the word typo.

# Replace multiple items in a Python list with the same value a_list = ['aple', 'ornge', 'aple', 'banana', 'grape', 'aple'] for i in range(len(a_list)): if a_list[i] in ['aple', 'ornge']: a_list[i] = 'typo' print(a_list) # Returns: ['typo', 'typo', 'typo', 'banana', 'grape', 'typo']

Similar to the for loop method shown earlier, we check whether or not an item is a typo or not and replace its value.

In the next section, youll learn how to replace multiple values in a Python list with different values.

Check out some other Python tutorials on datagy, including our complete guide to styling Pandas and our comprehensive overview of Pivot Tables in Pandas!

Replace Multiple Values with Multiple Values in a Python List

The approach above is helpful if we want to replace multiple values with the same value. There may be times where you want to replace multiple values with different values.

Looking again at our example, we may want to replace all instances of our typos with their corrected spelling. We can again use a for loop to illustrate how to do this.

Instead of using a single if statement, well nest in some elif statements that check for a values value before replacing.

# Replace multiple items in a Python list with the different values a_list = ['aple', 'ornge', 'aple', 'banana', 'grape', 'aple'] for i in range(len(a_list)): if a_list[i] == 'aple': a_list[i] = 'apple' elif a_list[i] == 'ornge': a_list[i] = 'orange' print(a_list) # Returns: ['apple', 'orange', 'apple', 'banana', 'grape', 'apple']

Need to check if a key exists in a Python dictionary? Check out this tutorial, which teaches you five different ways of seeing if a key exists in a Python dictionary, including how to return a default value.

Conclusion

In this tutorial, you learned how to use Python to replace items in a list. You learned how to use Python to replace an item at a particular index, how to replace a particular value, how to modify all values in a list, and how to replace multiple values in a list.

To learn more about Python list indexing, check out the official documentation here.

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