Скачать или смотреть How to Check if a Specific Number is Present in a File's Lines Using Python 20

Discover how to efficiently verify the presence of a specific number in file lines and process your data accordingly in Python.
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How to Check if a Specific Number is Present in a File's Lines Using Python 20

When working with files in Python, you may often need to check if certain values are present in the data. A common scenario is needing to identify if a specific number appears in the lines of a file. In this guide, we will discuss how to do just that using Python, focusing on an example where we need to check for the number 20 in a given file.

The Problem

You have a file named in.txt that contains several lines of data. Each line has multiple columns, with the last column being the one you need to check for the number 20. Your goal is to read this file, identify the presence of 20, and write the output to a new file called out.txt with a clear indication of whether or not the number is present in each line.

Example of in.txt

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

Expected Format of out.txt

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The Solution

To accomplish this task, you can utilize Python's with open() as method for file handling along with string manipulation methods to check the contents of each line. Below, we outline the step-by-step solution to implement this.

Step 1: Open the Input and Output Files

First, you need to open the input file (in.txt) for reading and the output file (out.txt) for writing. This is done using a nested with statement which ensures that the files are properly closed after their use.

Step 2: Read Through Each Line

In your loop, you will read each line from the input file and strip any extra spaces or newline characters for clean processing.

Step 3: Check the Last Column

Instead of checking if the string 20 exists anywhere in the line, you should specifically check if the line ends with 20. This can be achieved using the endswith() string method.

Step 4: Write Output Conditionally

For each line, if it ends with 20, you append the string twenty_number to that line in the output file. If it doesn't, you simply append none to indicate it wasn't found.

The Complete Code

Here's how the final code looks in Python:

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

Explanation of the Code

File handling: Using with open(), files are automatically closed after their block finishes execution.

String manipulation: The method strip() removes unnecessary spaces, and endswith() checks the last part of each line.

Conditional Writing: Depending on the presence of 20, the output is modified correspondingly.

Output from out.txt

After running the above script with the provided input file, your out.txt will look like this:

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

Conclusion

Using the endswith() method to specifically target the last column of your data proves to be an efficient way to check for specific numbers in files. This approach not only saves time but also ensures the accuracy of your data processing. By following the steps outlined in this guide, you can confidently handle similar tasks in your own Python projects.

Final Thoughts

If you encounter any similar challenges when working with files in Python, remember the concepts discussed in this post. Feel free to adapt the code snippets for other numerical checks or file formats as needed. Happy coding!