Exercises - Scripting Python for CLI tools

Exercises - Scripting Python for CLI tools#

These exercise should help you either reviewing or learning new shell commands. The exercises can be done localy on Linux, Mac or Windows 11 bash console.

1 Running Python statements from the command line#

We don’t need to open the interactive interpreter to run Python code. Instead, we can invoke Python with the command flag -c and the statement we want to run:

%%bash 
python -c "print(2+3)"

5

When and why is this useful?

2 Listing files#

A Python library called glob can be used to create a list of files matching a pattern, much like the ls shell command.

$ python

Python 3.7.6 (default, Jan  8 2020, 13:42:34) 
[Clang 4.0.1 (tags/RELEASE_401/final)] :: 
Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license"
for more information.

NOTE: run this locally, not possible to enter python shell in a jupyter notebook cell. AND you will like have a newer version of Python installed wich is fine! Python 3.10 or newer is recommended anyways

import glob
glob.glob('zipf/data/*.txt')

['zipf/data/dracula.txt',
 'zipf/data/frankenstein.txt',
 'zipf/data/jane_eyre.txt',
 'zipf/data/moby_dick.txt',
 'zipf/data/sense_and_sensibility.txt',
 'zipf/data/sherlock_holmes.txt',
 'zipf/data/time_machine.txt']

Using script_template.py as a guide, write a new script called my_ls.py that takes as input a directory and a suffix (e.g., py, txt, md, sh) and outputs a list of the files (sorted alphabetically) in that directory ending in that suffix.

The help information for the new script should read as follows:

$ python bin/my_ls.py -h

usage: my_ls.py [-h] dir suffix

List the files in a given directory with a given suffix.

positional arguments:
  dir         Directory
  suffix      File suffix (e.g. py, sh)

optional arguments:
  -h, --help  show this help message and exit

and an example of the output would be:

$ python bin/my_ls.py data/ txt

data/dracula.txt
data/frankenstein.txt
data/jane_eyre.txt
data/moby_dick.txt
data/sense_and_sensibility.txt
data/sherlock_holmes.txt
data/time_machine.txt

NOTE: we will not be including this script in subsequent chapters.

3 Sentence ending punctuation#

Our wordcount.py script strips the punctuation from a text, which means it provides no information on sentence endings. Using template.py and wordcount.py as a guide, write a new script called sentence_endings.py that counts the occurrence of full stops, question marks and exclamation points and prints that information to the screen.

Hint: String objects have a count method:

"Hello! Are you ok?".count('!')

1

When you’re done, the script should be able to accept an input file:

$ python bin/sentence_endings.py data/dracula.txt

Number of . is 8505
Number of ? is 492
Number of ! is 752

or standard input:

$ head -n 500 data/dracula.txt | python bin/sentence_endings.py

Number of . is 148
Number of ? is 8
Number of ! is 8

NOTE: we will not be including this script in subsequent chapters.

Contents