#067 Command Line Tools with begins
Using the begins library to write command line scripts without all the cruft.
Notes
The begins library replaces conventional argparse/main function pattern with a simple decorator. I found this in 20 Python Libraries You Aren’t Using (But Should), from which I’ve basically snaffled this example.
The following are functionally equivalent. First the traditional way:
import argparse
def add(a, b):
return a + b
if __name__ == '__main__':
parser = argparse.ArgumentParser(description="Add two numbers")
parser.add_argument('-a', help='First value', type=float, default=0)
parser.add_argument('-b', help='Second value', type=float, default=0)
args = parser.parse_args()
print(add(args.a, args.b))
And now using begins (python3 syntax):
import begin
@begin.start(auto_convert=True)
def add(a: 'First value' = 0.0, b: 'Second value' = 0.0):
""" Add two numbers """
print(a + b)
Setup
Use the requirements.txt to install begins:
pip install -r requirements.txt
The examples that follow use both python 2 and python 3. the begins library needs to installed for both.
Running the Examples
add.py is the conventional approach, with argparse and an explicit main section:
$ python add.py -h
usage: add.py [-h] [-a A] [-b B]
Add two numbers
optional arguments:
-h, --help show this help message and exit
-a A First value
-b B Second value
$ python add.py -a 3 -b 4
7.0
add_with_begins.py uses begins and python 2 compatible syntax:
$ python add_with_begins.py -h
usage: add_with_begins.py [-h] [--a A] [--b B]
Add two numbers
optional arguments:
-h, --help show this help message and exit
--a A, -a A (default: 0.0)
--b B, -b B (default: 0.0)
$ python add_with_begins.py -a 3 -b 4
7.0
add_with_begins3.py uses begins and python 3 compatible syntax:
$ python3 add_with_begins3.py -h
usage: add_with_begins3.py [-h] [--a A] [--b B]
Add two numbers
optional arguments:
-h, --help show this help message and exit
--a A, -a A First value (default: 0.0)
--b B, -b B Second value (default: 0.0)
$ python3 add_with_begins3.py -a 3 -b 4
7.0
Credits and References
- begins - pypi
- begins - GitHub
- 20 Python Libraries You Aren’t Using (But Should)