One 、 Preface
What I want to introduce today click[2] It's a familiar way to play around the command line . Command line programs are essentially defining parameters and processing parameters , The logic of processing parameters must be related to the defined parameters . Can we use functions and decorators to realize the relationship between processing parameter logic and defining parameters ？ and click It's exactly in this way that .
This series uses... By default Python 3 Explain as an interpreter .
If you are still using Python 2, Please pay attention to the differences between the syntax and the use of the library ~
Two 、 Introduce
click Is a code with as little code as possible 、 To create graceful command line programs in a combined way Python package . It's highly configurable , It can also be used out of the box .
It's designed to make the process of writing command-line tools quick and fun , It can also prevent the failure to achieve the expected CLI API A sense of frustration . It has the following three characteristics ：
3、 ... and 、 Quick start
3.1 Business logic
First define the business logic , Don't you feel some disbelief ？
Whether it's argparse still docopt, Business logic is all put in the last step , but click But in the first step . Think about it click This way is more in line with people's thinking ？ No matter what command-line framework you use , Our ultimate concern is to implement business logic , Other energy savings are less .
Let's take the official example , To introduce click Usage and philosophy of . Suppose the input to the command line program is name and count, The function is to print the name of a specified number of times .
So in hello.py in , It's easy to write the following code ：
def hello(count, name):
"""Simple program that greets NAME for a total of COUNT times."""
for x in range(count):
click.echo('Hello %s!' % name)
The logic of this code is very simple , It's a cycle count Time , Use click.echo Print name. among ,click.echo and print It's similar , But it's more powerful , Can handle Unicode and Binary data .
3.2 Defining parameters
Obviously , We need to target count and name To define their corresponding parameter information .
count Corresponding to command line options --count, The type is number , We hope that when we do not provide parameters , The default value is 1
name Corresponding to command line options --name, Type is string , We hope that when we do not provide parameters , Can give a hint
Use click, It can be written as follows ：
from click import click
@click.command() @click.option('--count', default=1, help='Number of greetings.') @click.option('--name', prompt='Your name', help='The person to greet.') def hello(count, name): ...
In the example above ：
No matter the way of decorating 、 Or default behavior ,click It's all like its introduction , Let people write as little code as possible , Make the whole process fast and fun .
3.3 Code hacking
Use click It's very simple , Let's summarize the above code , To have a clearer understanding of ：
# hello.py
import click
@click.command()
@click.option('--count', default=1, help='Number of greetings.')
@click.option('--name', prompt='Your name',
help='The person to greet.')
def hello(count, name):
"""Simple program that greets NAME for a total of COUNT times."""
for x in range(count):
click.echo('Hello %s!' % name)
if __name__ == '__main__':
hello()
If we specify times and names ：
$ python3 hello.py --count 2 --name Eric
Hello Eric!
Hello Eric!
If we don't specify anything , You will be prompted to enter a name , And default output once ：
$ python3 hello.py
Your name: Eric
Hello Eric!
We can also go through --help Parameter to view automatically generated help information ：
Usage: hello.py [OPTIONS]
Simple program that greets NAME for a total of COUNT times.
Options:
--count INTEGER Number of greetings.
--name TEXT The person to greet.
--help Show this message and exit.
Four 、 Summary
click The idea is very simple , Define processing functions , Define parameters through its decorator . The great thing about using decorators is to combine the two steps of definition and binding into one step , Make the whole process silky .
click Except for Pythonic This method makes the implementation of the command-line program more elegant and easy to use , There are also offers argparse and docopt All need powerful functions .
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