Python初学者教程：如何使用Python构建简单的命令行工具？

原创比眉伴天荒 2024-12-21 08:18 29阅读 0赞

构建一个简单的命令行工具，你可以遵循以下步骤，这个例子我们将创建一个简单的计算器：

1. **设置环境**：
   在你的Python环境中安装`argparse`库。这是处理命令行参数的标准库。

```bash
pip install argparse
```

2. **编写脚本**：
   创建一个`.py`文件，比如`calculator.py`，然后编写脚本代码。

```python
import argparse

def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

def multiply(x, y):
    return x * y

def divide(x, y=None):
    if y == None:
        return "Error: Division by zero is not allowed."
    else:
        try:
            return x / y
        except ZeroDivisionError:
            return "Error: Division by zero is not allowed."

def main():
    parser = argparse.ArgumentParser(description='Simple calculator command line tool.')
    subparsers = parser.add_subparsers(title='Operations', dest='operation')

add_parser = subparsers.add_parser('add', help='Add two numbers'))
    add_parser.add_argument('num1', type=int, help='First number to be added')
    add_parser.add_argument('num2', type=int, help='Second number to be added')

subtract_parser = subparsers.add_parser('subtract', help='Subtract one number from another'))
    subtract_parser.add_argument('num1', type=int, help='Number to be subtracted')
    subtract_parser.add_argument('num2', type=int, help='Number to be subtracted from')

multiply_parser = subparsers.add_parser('multiply', help='Multiply two numbers'))
    multiply_parser.add_argument('num1', type=int, help='First number to be multiplied')
    multiply_parser.add_argument('num2', type=int, help='Second number to be multiplied')

divide_parser = subparsers.add_parser('divide', help='Divide one number by another'))
    divide_parser.add_argument('num1', type=float, help='Number to be divided')
    divide_parser.add_argument('num2', type=float, help='Number to be divided from')

args = parser.parse_args()
    if args.operation == 'add':
        result = add(args.num1, args.num2))
    elif args.operation == 'subtract':
        result = subtract(args.num1, args.num2))
    elif args.operation == 'multiply':
        result = multiply(args.num1, args.num2))
    elif args.operation == 'divide':
        if args.num2 != 0:
            result = divide(args.num1, args.num2))
        else:
            result = "Error: Division by zero is not allowed."
    print(result)

if __name__ == "__main__":
    main()
```

现在你可以通过命令行来使用这个计算器工具，例如：

```bash
python calculator.py add 5 7
```

这将输出计算结果12。