Скачать или смотреть How to Subtract Every Item from a List in Python

Learn how to subtract each item from a list in Python with this step-by-step guide. Get the final result with simple code!
---
This video is based on the question https://stackoverflow.com/q/66672163/ asked by the user 'ARandomPro' ( https://stackoverflow.com/u/14859960/ ) and on the answer https://stackoverflow.com/a/66672206/ provided by the user 'Cory Kramer' ( https://stackoverflow.com/u/2296458/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to subtract every item of a list

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Subtract Every Item from a List in Python

When working with lists in Python, you might encounter a situation where you want to calculate the cumulative subtraction of each item from the list. This can be a bit trickier than simply adding all the numbers together. In this guide, we'll uncover how to effectively achieve this using Python code, leading us to a final result through a series of subtractions.

The Problem

Let's say we have a list of numbers and we want to subtract each subsequent item from the first item sequentially. For example, given the list:

[[See Video to Reveal this Text or Code Snippet]]

We want to perform the following operations:

100 - 20 = 80

80 - 5 = 75

75 - 15 = 60

So, the output we want is 60.

A novice might try using the built-in sum() function, which adds all numbers together instead of subtracting, resulting in the wrong output. This leads us to the question: How do we achieve our desired subtraction instead?

The Solution

To solve the problem, we can take a more systematic approach. Instead of manually performing each subtraction, we can use Python's capabilities to streamline the process. Here’s how we can do it:

Step-by-Step Approach

Access the First Element: Start by taking the first item of the list as your base number for the subtraction.

Sum the Remaining Items: Use the sum() function to calculate the total of all remaining items in the list.

Perform the Subtraction: Subtract the total from the first element.

The Code Implementation

Here’s how you can put this into action with Python code:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

x[0]: This retrieves the first item from the list, which in our case is 100.

sum(x[1:]): This computes the total of the remaining items in the list, which are 20, 5, and 15. Their sum equals 40 (20 + 5 + 15).

Finally, 100 - 40 gives us the desired result of 60, which we then print to the console.

Conclusion

Incorporating this simple technique allows you to effectively subtract each item in a list sequentially starting from the first. By utilizing the sum() function in combination with list indexing, you streamline your code and make it more efficient.

Try implementing this code in your own Python projects, and you'll find it both useful and powerful when dealing with similar problems. Happy coding!