AaronLaw/learn-more-python3-the-hard-way

Readme

This is a long-running project that I will go to (re)implement some UNIX commands with a book "Learn more Python the hard way" to learn to program better.

3 things to be bear in mind:

1. process
2. creativity
3. quality

Quick hacks

Organization: program comments should be put in README rather than be put in the python script. (a.k.a. don't make dead code nor unintentional comments in the script.)

Dealing with command line arguments

• on research how to get command line arguments from a user
  • with sys.argv
  • with argparse
  • with click
    • try more options with click
  • extend the add(a, b) to add(a, b, ..., n) (a.k.a. passing *args to function)

Some basics functions which all CLIs have are:

• An argument. (positional argument)
• An option, which is an optional parameter
• A flag, this is a special option which enables or disables a certain function. One of the most common flags is –help.

reference:

• how to work with sys.argv?
  • Google: sys.argv -> How to use sys.argv in Python - GeeksforGeeks for study on sys.argv, argparse, click
• how to work with argparse?
  • Google: argparse -> https://docs.python.org/3/library/argparse.html
• how to add program description with click? (e.g. "this program adds 2 given numbers...")
  • Google: python click program description -> The Definitive Guide to Python Click
• how to work with *args with Click?
  • Google: click *args -> Variadic Arguments
• given a list of numbers. how to subtract from the 1st element, then 2nd element, then the nth element?
  • poe: python doing subtraction in a list elements. from first element - second element - thrid element

for doing subtraction elements in a list: (answered by poe)

numbers = [10, 5, 3, 1]
result = numbers[0]  # Set the initial result to the first element

for i in range(1, len(numbers)):
    result -= numbers[i]  # Subtract each subsequent element

print(result)  # Output: 1

or

numbers = [10, 5, 3, 1]
result = numbers[0] - sum(numbers[1:])

print(result)  # Output: 1

The concepts of click

click uses decorator to wrap function to a Command ¹ => I write function 1st, then make it into Command.

Reflection

Finding out what blocks me to work on:

• At first, I am lazy to figure out / to study how argparse works.
• When I try to make a MVP with Click, the script doesn't work at first. -> I am afraid of reading onlarge pages of documentation of any 3rd party projects.
  • The solution is quite simple: The concept behind Click is turing python function into a Command with the @click decorator.
  • the problem of mine is: I have an option --verbose but I haven't notice I have to put it in function signature at 1st because I have no idea the concept behind Click is turning python function into a Command (it is because I haven't read through Click's documentation):
    • def add(first, second) => def add(first, second, verbose=False)

cat

Reflection

Finding out what blocks me to work on:

Footnotes

1. Python Command Line Tools by Noah Gift ↩