working-with-files.md

Working with Files and Folders

This section covers the following topics:

• Reading and writing files
• Listing and traversing files in a directory
• Matching files based on wildcards
• Working with temporary files

Suggested reading:

• Working with Files section in Python Practice Book
• os module on Python-module-of-the-week
• os.path module on Python-module-of-the-week
• glob module on Python-module-of-the-week
• shutil module on Python-module-of-the-week

Questions

• Write a program copyfile.py to copy one file to another. It should accept 2 filenames as arguments and copies the first one into the second.

  $ python copyfile.py a.txt b.txt

• Write a program head.py that takes a filename as command-line argument and prints first 5 lines of it.

  $ python head.py one-to-ten.txt 1 2 3 4 5

• Write a program grep.py that takes a pattern and a filename arguments and prints all the lines in the file that contain given pattern.

  $ python grep.py o numbers.txt 1 one 2 two 4 four

• Write a program wrap.py that takes filename and width as command-line arguments and wraps the lines longer than given width.

  $ python wrap.py numbers.txt 5 1 one 2 two 3 thr ee 4 fou r 5 fiv e

• Write a program ls.py that takes path to a directory as command-line argument and prints all the files in that directory. If no argument is specified, it should list the files in the current directory.

  $ python ls.py

• Write a program mostrecent.py to find the most recently modified file in the given directory. The program should accept the directory name as command-line argument and print path to the file (not just filename) that is most recently modified file.

  $ python mostrecent.py logs/ logs/access.log

  $ python mostrecent.py /tmp /tmp/a.txt

• Write a program find-matching-files.py to find files recursively in a directory tree matching given wildcard pattern. The program should accept the directory and the pattern as command-line argument.

  $ python find-matching-files.py project '*.py' project/init.py project/a.py project/_util.py project/submodule/init.py project/submodule/b.py

  $ python find-matching-files.py project '?.py' project/a.py project/submodule/b.py

• Write a program find-large-files.py to find files recursively in a directory tree that are larger than given size. The program should accept the directory and the size as command-line argument. The size can be also be specified with K, M and G suffix for KB, MB and GB respectively.

  $ python find-large-files.py logs 100000 logs/access.log logs/error.log

  $ python find-large-files.py logs 100K logs/access.log logs/error.log

  $ python find-large-files.py logs 2M logs/access.log