Passing command line arguments to functions and methods with python-fire

2023-09-26 python

python-fire is a library to create CLI tools from Python objects.

$ pip install fire

Just wrap with fire.Fire() to pass command line arguments to functions and methods.

$ cat main.py
import fire

class FizzBuzz:
  def fizzbuzz(self, num):
    ret = ""
    if num % 3 == 0:
      ret += "fizz"
    if num % 5 == 0:
      ret += "buzz"
    if len(ret) != 0:
      return ret
    return str(num)

  def fizzbuzzs(self, nums):
    return [self.fizzbuzz(num) for num in nums]
    
if __name__ == '__main__':
  fire.Fire(FizzBuzz)

$ python main.py fizzbuzzs --nums="[2,21,30]"
2
fizz
fizzbuzz

Command line arguments are evaluated to strings, numbers, lists, etc. by ast.literal_eval().

import ast
root = ast.parse('[{"a":100}]', mode='eval')
print(type(ast.literal_eval(root))) # <class 'list'>

Besides, you can run REPL or display trace.

$ python main.py -- --interactive
>>> FizzBuzz().fizzbuzz(10)
'buzz'

$ python main.py fizzbuzzs --nums="[2,21,30]" -- --trace
Fire trace:
1. Initial component
2. Instantiated class "FizzBuzz" (xxx/main.py:3)
3. Accessed property "fizzbuzzs" (xxx/main.py:14)
4. Called routine "fizzbuzzs" (xxx/main.py:14)