# 2211-pythonAdvanced

**Repository Path**: hj00/2211-python-advanced

## Basic Information

- **Project Name**: 2211-pythonAdvanced
- **Description**: python进阶
- **Primary Language**: Python
- **License**: MIT
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2022-11-28
- **Last Updated**: 2023-04-01

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# 2211-pythonAdvanced

>python进阶历程

## pip常用命令
```shell
pip install xxx
pip install xxx==x.x.x
pip install -U xxx
pip list
pip search xxx
pip install -r requirements.txt
pip uninstall xxx
pip uninstall all
```

## 虚拟环境
### 官方 venv
```shell
c:\Python35\python -m venv c:\path\to\myenv # 无环境变量
python -m venv c:\path\to\myenv # 有环境变量
<venv>\Scripts\activate.bat # 激活
```

### 第三方 pipenv
```shell
pip install pipenv
pipenv -version
cd d:\dir
pipenv install
pipenv install xxx
pipenv install -r /path/requirements.txt
pipenv lock -r # 提取依赖库，精准迁移
pipenv shell # 激活方式1
pipenv run python /path/xx.py # 激活方式2
pipenv uninstall xxx
pipenv uninstall all
```

## 匿名函数
```python
add = lambda n, m: n + m
add(2, 3) # 调用匿名函数
```

## 序列操作
### map
```python
myList = [1,2,3,4,5]
list(map(lambda x:x*2,myList)) # [2, 4, 6, 8, 10]
```
### filter
```python
myList = [1,2,3,4,5]
list(filter(lambda x:x%2,myList)) # [1, 3, 5]
```
### enumerate
```python
myList = ['enumerate','增加索引']
list(enumerate(myList)) # [(0, 'enumerate'), (1, '增加索引')]
```

## property属性
>防止从类或对象的外部修改内部属性，只能通过定义特定的方法修改
```python
class Person:
    def __init__(self):
        self.__age = 9
    @property
    def age(self):
        return self.__age
    @age.setter
    def age(self, val):
        self.__age = val
person = Person()
person.age=9
print(person.age) # 8
```
等价于
```python
class Person:
    def __init__(self):
        self.__age = 9
    def getter(self):
        return self.__age
    def setter(self, val):
        self.__age = val
    age = property(getter, setter)
person = Person()
person.age=9
print(person.age) # 8
```

## 特殊语法
### 变量赋值
```python
a, b = 1, 2
a, b = b, a
```
### 连续赋值
```python
a = b = None
```
### 连续比较
```python
a, b = 1, 3
if 0 < a < b < 10:
    print('pass')
```
### 装包解包
```python
a, b, c = 1, 2, 3
t = a, b, c # tuple:(1,2,3)
d, e, f = t
```
**高级装包解包**
```python
a, b, c = 1, [2,3], 4
t = a, *b, c # (1,2,3,4)
d, e, *f = t # d=1, e=2, f=[3,4]
```

## 推导表达式
### 列表推导表达式
```python
myList = [1, 2, 3, 4, 5]
myList2 = [i for i in myList if i % 2] # 过滤奇数
myList3 = [i * 2 for i in myList] # 每个元素乘2
names = ['张三', '李四', '王老六']
names2 = [name for name in names if len(name) == 3] # 过虑长度为3的名字
```
### 字典推导表达式
```python
myDic = {'k1': 1, 'k2': 2, 'k3': 3}
myDic2 = {k: v for k,v in myDic.items() if v%2} # 过滤值是奇数的子项
myDic3 = {k: v*2 for k,v in myDic.items()} # 所有子项值乘2
```
### 集合推导表达式
```python
mySet = {1, 2, 3, 4, 3, 5} # 集合内没有重复元素，若有则自动去重
mySet2 = {i for i in mySet if i%2}
mySet3 = {i for i in mySet}
```
### 生成器推导表达式（嵌套）
```python
"""求笛卡尔积"""
m = [1, 3, 5]
n = [2, 6]
cartesianProduct = [(i, j) for i in m for j in n]
# [(1, 2), (1, 6), (3, 2), (3, 6), (5, 2), (5, 6)]
```