# Best feature of Python | List Comprehensions | Summary and Q&A

106.9K views
August 7, 2020
by
Lex Fridman
Best feature of Python | List Comprehensions

## TL;DR

Python list comprehensions allow you to define one list in terms of another, making programming enjoyable and elegant.

## Key Insights

• 👂 List comprehensions are a powerful and elegant feature of Python, allowing you to define new lists based on existing ones.
• 🔁 They combine a for loop, a function, and a filter condition in a concise notation.
• 👂 List comprehensions are more enjoyable and readable, making programming in Python a pleasant experience.
• 🥰 Python's list comprehension notation is considered the best feature of the language, as it can make programmers fall in love with it.
• 👂 While map and filter functions can achieve similar results, list comprehensions are preferred for their simplicity and elegance.
• 👂 The walrus operator, another controversial feature in Python, complements list comprehensions well.
• 👂 List comprehensions allow for faster execution when dealing with smaller lists and situations where speed is crucial.

## Transcript

this is a list comprehension that allows you to define one list in terms of another list and is reminiscent of set notation from mathematics the elegance simplicity and power of this notation makes it in my opinion the best feature of python now what does it mean to be a best feature of a programming language to me it's a feature that makes you fal... Read More

### Q: What is a list comprehension and how does it work?

A list comprehension is a concise way to define a new list in Python based on an existing list, using a for loop and a function. It iterates over each element of the input list and applies the specified function to it.

### Q: Can you provide an example of a list comprehension?

Sure! Let's say we have an input list "nums" containing [1, 2, 3, 4]. To square each element of the nums list, you can use the list comprehension [x * x for x in nums], resulting in [1, 4, 9, 16].

### Q: How can we add a filter condition to a list comprehension?

To keep only the even numbers from the nums list, you can add a conditional expression to the list comprehension like [x * x for x in nums if x % 2 == 0]. This will give you the squared values of the even elements, resulting in [4, 16].

### Q: How does a list comprehension compare to alternatives like for loops, map, and filter?

List comprehensions are more elegant, readable, and Pythonic compared to alternative methods. They provide a concise and powerful notation for creating new lists. While alternatives like for loops and map/filter functions can achieve similar results, list comprehensions are preferred for their simplicity and readability.

### Q: What is a list comprehension and how does it work?

A list comprehension is a concise way to define a new list in Python based on an existing list, using a for loop and a function. It iterates over each element of the input list and applies the specified function to it.

## More Insights

• List comprehensions are a powerful and elegant feature of Python, allowing you to define new lists based on existing ones.

• They combine a for loop, a function, and a filter condition in a concise notation.

• List comprehensions are more enjoyable and readable, making programming in Python a pleasant experience.

• Python's list comprehension notation is considered the best feature of the language, as it can make programmers fall in love with it.

• While map and filter functions can achieve similar results, list comprehensions are preferred for their simplicity and elegance.

• The walrus operator, another controversial feature in Python, complements list comprehensions well.

• List comprehensions allow for faster execution when dealing with smaller lists and situations where speed is crucial.

• Generator expressions, an alternative to list comprehensions, are suitable for larger or infinite ranges and for creating iterable objects.

## Summary

This video discusses the concept of list comprehension in Python and highlights why it is considered the best feature of the language. List comprehension allows you to define one list in terms of another list using a concise and elegant notation. It involves a for loop over an input list and a function that computes something for each element in the list. Additionally, there is a filter conditional that only keeps elements that pass a certain condition. The video compares list comprehension to alternative approaches such as for loops, map and filter functions, and showcases its advantages in terms of readability and simplicity.

### Q: What is list comprehension?

List comprehension is a notation in Python that allows you to define a new list based on another list. It consists of a for loop over an input list and a function that computes something for each element in the list. It also includes a filter conditional that selects only the elements that pass a specific condition.

### Q: Why is list comprehension considered the best feature of Python?

List comprehension is often regarded as the best feature of Python due to its elegance, simplicity, and power. It has the ability to make programmers fall in love with the language and enjoy programming in it for many years. The concise and expressive notation of list comprehension makes it easy to understand and write complex operations in a simple manner.

### Q: How does list comprehension work?

List comprehension works by iterating over an input list and applying a function to each element in the list. The output of the function is then used to generate a new list. Additionally, a filter conditional can be applied to only include elements that pass a certain condition. The result is a new list that is created using a concise and readable notation.

### Q: Can the same results be achieved using alternative approaches in Python?

Yes, the same results can be achieved using alternative approaches such as for loops or the map and filter functions available in Python. However, these approaches are often more verbose and less readable compared to list comprehension. While they may provide similar functionalities, list comprehension stands out for its elegance and Pythonic nature.

### Q: How does list comprehension compare to alternative approaches like map and filter functions?

List comprehension is considered more elegant and readable compared to alternative approaches like map and filter functions. While both approaches can achieve similar results, list comprehension offers a more concise and expressive notation. The for loop, function, and filter conditional are all combined into a single line, making the code easier to understand and maintain.

### Q: What is the benefit of using the filter conditional in list comprehension?

The filter conditional in list comprehension allows you to selectively include or exclude elements from the input list based on a specific condition. This makes it easy to filter out elements that do not meet certain criteria and only keep the ones that pass the condition. It provides flexibility and control over the elements included in the resulting list.

### Q: What are the advantages of using list comprehension over other approaches?

List comprehension offers several advantages over other approaches. Firstly, it provides a more elegant and readable notation, making code easier to understand and maintain. Secondly, it allows for concise and expressive expressions, reducing the need for multiple lines of code. Lastly, list comprehension is considered a Pythonic feature, aligning with the design principles and philosophy of the Python language.

### Q: Can you provide an example of using list comprehension?

Certainly! Let's consider an input list called "nums" with elements [1, 2, 3, 4]. To square each element of "nums" using list comprehension, we can use the expression "x * x for x in nums". The result will be a new list containing [1, 4, 9, 16]. This example showcases the simplicity and power of list comprehension in generating a new list based on the elements of an input list.

### Q: How can a filter be added to list comprehension?

To add a filter to list comprehension, you can include a conditional expression after the loop and before the function in the notation. For example, to keep only the even numbers from the input list "nums", you can modify the list comprehension expression to "x * x for x in nums if x % 2 == 0". This will result in a new list containing [4, 16] as it only includes the elements that pass the filter condition.

### Q: Is list comprehension more efficient than generator expressions?

List comprehension and generator expressions serve different purposes and have different efficiency characteristics. List comprehension creates a list object and computes all the elements in the list, storing the entire list in memory. On the other hand, generator expressions store just the iterable object and compute each element one at a time as it's being queried. If the size of the list is not excessively large and multiple iterations are needed, list comprehension is usually faster. However, for large or infinite sequences, or when memory efficiency is crucial, generator expressions are a better choice.

### Q: When should I use list comprehension versus generator expressions?

List comprehension is the default choice for most situations, especially when the size of the list is not excessively large and when multiple iterations over the list are required. It is also preferable when you need different list methods like slicing notation. Generator expressions, on the other hand, are suitable when dealing with large or infinite sequences, or when memory efficiency is crucial. Generator expressions often provide a more efficient way to compute the elements of a sequence one at a time, without storing the entire list in memory.

## Takeaways

List comprehension is a powerful and elegant feature of Python that allows you to define a new list based on another list using a concise and readable notation. It offers advantages in terms of simplicity, readability, and expressiveness compared to alternative approaches such as for loops or map and filter functions. List comprehension is the preferred choice when the size of the list is not excessively large and multiple iterations are needed. Generator expressions, on the other hand, are more suitable for large or infinite sequences and when memory efficiency is crucial.

## Summary & Key Takeaways

• List comprehensions in Python allow you to define a new list based on another list, using a for loop and a function.

• You can add a filter condition to a list comprehension to only keep elements that pass the condition.

• List comprehensions are more elegant, readable, and Pythonic compared to alternative methods like for loops, map, and filter functions.