编程-python

# python

`wget https://www.python.org/ftp/python/3.7.3/python-3.7.3-amd64.exe`

## 配置环境变量

将如下目录配置到PATH中即可
  - python.exe所在的目录
  - python.exe所在的目录下的Scripts

### 使用国内pypi镜像

#### 方式一：临时使用

```shell
pip3 install -i https://mirrors.aliyun.com/pypi/simple/ selenium
pip3 install -i https://mirrors.aliyun.com/pypi/simple/ mysql-connector
```

#### 方式二：永久使用

for windows

```bat
mkdir %APPDATA%\pip
cd %APPDATA%\pip
type nul > pip.ini
echo [global] > pip.ini
echo timeout=6000 >> pip.ini
echo index-url=https://mirrors.aliyun.com/pypi/simple/ >> pip.ini
echo [install] >> pip.ini
echo trusted-host=https://mirrors.aliyun.com >> pip.ini
```

for linux

将如下内容放到~/.pip/pip.conf文件中即可

```text
[global]
index-url=http://mirrors.aliyun.com/pypi/simple/

[install]
trusted-host=mirrors.aliyun.com
```

## 问题

### C:\Users\Administrator\AppData\Local\Programs\Python\Python37\python.exe: No module named pip

```
python -m ensurepip
```

解决办法见 https://blog.csdn.net/weixin_44935307/article/details/127501512

### 升级 pip: You are using pip version 19.0.3, however version 23.1.2 is available. You should consider upgrading via the 'python -m pip install --upgrade pip' command.

```
# 使用如下
python -m pip install -i https://mirrors.aliyun.com/pypi/simple/ --upgrade pip
# 而非
python -m pip install  --upgrade pip
```

## 编码

### 在给一个自定义对象的某字段赋值时做些其它操作

```python
import jsons

class Hello:
    code: int
    msg: str

def __setattr__(self, name, value):
        print('here', name, value)
        if name == 'msg':
            # 每执行一次，就追加一次
            self.__dict__.__setitem__(name, value + " -- updated")
        else:
            self.__dict__.__setitem__(name, value)

def test_type_hello():
    hello = Hello()
    # 会导致调用__setattr__
    hello.code = 100
    # 会导致调用__setattr__
    hello.msg = 'abcdef'
    assert 'abcdef' in hello.msg
    assert '-- updated' in hello.msg
    json_data = jsons.dump(hello)
    # 会导致调用__setattr__
    hello_de = jsons.load(jsons.dump(json_data), Hello)
    assert 'abcdef' in hello_de.msg
    assert '-- updated' in hello_de.msg
```