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Effectively Managing Files

In the Terminal Using Python

Python is not only popular as a programming language for application development but also quite powerful for automation tasks in the terminal. Here’s a little useful guide to using one-liner Python commands that can help us work efficiently in the terminal.

Moving Files with Similar Names Using Python

Suppose you have several files with similar names like app01.py, app02.py, and so on. You want to move all of them to a specific directory. Typically, you would use the wildcard * with the mv command in the terminal, but Python can also accomplish this with additional flexibility.

Here’s a one-liner Python command to move all files starting with "app" and ending with ".py" to the target directory:

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python -c 'import glob, shutil; [shutil.move(f, "/path/to/target") for f in glob.glob("app*.py")]'

Explanation:

  • -c allows you to provide a line of Python code to be executed. It enables you to run Python commands directly from the command line without needing to create a separate script file.
  • glob.glob("app*.py") searches for all files matching the pattern "app*.py".
  • shutil.move(f, "/path/to/target") moves the found files to the target directory (/path/to/target).

Replacing Text in a File Easily

Sometimes, you need to replace specific text within a file. This command allows you to perform search and replace directly in the file without opening an editor:

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python -c 'import fileinput; [line.replace("old", "new") for line in fileinput.input("file.txt", inplace=True)]'

Explanation:

  • fileinput.input("file.txt", inplace=True) reads the file and allows in-place editing.
  • line.replace("old", "new") replaces all occurrences of the text "old" with "new" in each line.

Counting the Number of Lines in a File

Want to know how many lines are in a file without using wc -l? Use this Python command:

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python -c 'print(sum(1 for _ in open("file.txt")))'

Explanation:

  • sum(1 for _ in open("file.txt")) counts the number of lines in the file.

Sorting and Removing Duplicates from Text Files

If you want to sort and remove duplicates in a single line from a file, this command can help:

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python -c 'print(" ".join(sorted(set(line.strip().split()) for line in open("file.txt"))))'

Explanation:

  • line.strip().split() breaks the line into words and removes leading/trailing whitespace.
  • set() removes duplicate elements, and sorted() arranges the remaining elements.
  • " ".join(...) combines the processed words back into a single line.

Finding Specific Patterns in a File (Similar to Grep)

To search for lines in a file that match a specific pattern, use this command:

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python -c 'import sys; [print(line) for line in open("file.txt") if "pattern" in line]'

Explanation:

  • The condition if "pattern" in line checks for matches in each line.
  • print(line) prints the matching lines.

Displaying a List of Large Files in a Directory

If you want to find files larger than 5 MB in a specific directory, use this code:

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python -c 'import os; [print(f) for f in os.listdir() if os.path.isfile(f) and os.path.getsize(f) > 5 * 1024 * 1024]'

Explanation:

  • os.listdir() searches for all files in the current directory.
  • os.path.getsize(f) returns the size of the file in bytes.
  • Files larger than 5 MB will be printed in the terminal.

Counting the Number of Words in a File

To count the total number of words in a file, Python can do this quickly:

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python -c 'print(sum(len(line.split()) for line in open("file.txt")))'

Explanation:

  • len(line.split()) counts the number of words in each line.
  • The outer sum(...) adds up the total word count from each line.

Python’s versatility makes it a great choice for both simple and complex automation tasks.