### 函式


```python
varibal = {
    'a': 100,
    'b': 100,
    'c': 200
}
```


```python
varibal['a']
```




    100




```python
varibal.items()
```




    dict_items([('a', 100), ('b', 100), ('c', 200)])




```python
#尋找value的值為100的key值
[key for key, value in varibal.items() if value == 100]
```




    ['a', 'b']



#### 函式 - 抽象概念


```python
def get_keys(dict_varibal,value):
    return [k for k, v in dict_varibal.items() if v == value]
```


```python
get_keys(varibal,200)
```




    ['c']



#### 函式是組織好的，可重複使用的，能夠完成特定功能的程式碼塊，它是程式碼塊的抽象。


```python
get_keys({'a': 40}, 40)
```




    ['a']



#### 位置引數是不可以交換位置的


```python
def get_keys(dict_varibal,value):
    return [k for k, v in dict_varibal.items() if v == value]
```

- get_keys 函式名
- ()中為引數：dict_varibal——形參，呼叫的時候傳遞的值才是實參
- return 是返回值

    1、位置引數
    2、關鍵字引數，可以不按照順序去寫


```python
get_keys(dict_varibal={'a':40},value=40)
```




    ['a']




```python
get_keys(value=40,dict_varibal={'a':40})
```




    ['a']



### 函式通過引數獲取我們傳遞的值，函式中改變了引數的值，那麼我們傳遞進去的值會改變麼？


```python
def test(varibal):
    varibal = 100
    return varibal
```


```python
var = 1
test(var)
```




    100




```python
#var變數的值沒有改變
print(var)
```

    1
    


```python
def test(varibal):
    varibal.append(100)
    return varibal
```


```python
var = []
test(var)
```




    [100]




```python
#var變數的值發生了改變
print(var)
```

    [100]
    

#### 不建議對可變型別在函式內進行更改，建議用函式返回值進行重新賦值


```python
def test(varibal):
    temp = varibal.copy()
    temp.append(100)
    return temp
```


```python
var = []
var = test(var)
```




    [100]




```python
var
```




    []



### 引數的收集


```python
#*args收集位置引數, **kwargs收集關鍵字引數
def test(name, age, *args, **kwargs):
    print(name, age, *args, **kwargs)
```


```python
test('wang', 12)
```

    wang 12
    


```python
test('wang', 12, 23, 'lkl',[23,34])
```

    wang 12 23 lkl [23, 34]
    


```python
dict_varibal = {
    'weight' : 120,
    'height' : 175
}
test('wang', 12, dict_varibal)
```

    wang 12 {'weight': 120, 'height': 175}
    

#### 【重要】裝飾器


```python
a = 10
b = [12,12]

def test():
    print('test')

c = test
```

#### 可以把函式賦值給一個變數


```python
c.__name__
```




    'test'




```python
def test(func):
    return func

def func():
    print('func run')

f = test(func)
f.__name__
f()
```

    func run
    

#### 函式可以當做函式的返回值進行返回


```python
import random
#返回一個從0到1的浮點值
def test():
    return round(random.random(), 3)
```


```python
# 函式返回的浮點值保留三位有效數字

```


```python
test()
```




    0.112



### Python中的另一個語法糖，裝飾器


```python
#返回一個從0到1的浮點值
@decorator
def test():
    return random.random()

@decorator
def test_two():
    return random.random()*10
```


```python
def decorator(func):
    def wrapper(*args,**kwargs):
        # do something
        return round(func(*args,**kwargs), 3)  
    return wrapper
```


```python
#該語句完全等價於裝飾器@decorator的寫法
# f = decorator(test)
```


```python
f()
```




    0.18173988944007524




```python
f.__name__
```




    'wrapper'




```python
test.__name__
```




    'wrapper'




```python
test()
```




    0.033




```python
test_two()
```




    2.714



### 類


```python
class Person:
    def __init__(self, name, age):
        self._name = name
        self._age = age
        
    def get_name(self):
        return self._name
    
    def rename(self, new_name):
        self._name = new_name
```

#### 初始化函式中，self後面的是例項化物件的屬性，加下劃線的意思是，代表這個屬性是私有的，不應該訪問


```python
s = 'hello world'
s.center(12)
```




    'hello world '




```python
p = Person('wang', 12)
```


```python
p.get_name()
```




    'wang'




```python
p.rename('wang lei')
```


```python
p.get_name()
```




    'wang lei'




```python
p_2 = Person('li', 11)
p_2.get_name()
```




    'li'



#### pass代表什麼都不做，只是佔個位而已


```python
# class Student(Person):
    # pass
```


```python
class Student(Person):
    def set_score(self, score):
        self._score = score
    
    def get_score(self):
        return self._score
```


```python
s = Student('liu', 24)
s.get_name()
```




    'liu'




```python
s.set_score(100)
```


```python
s.get_score()
```




    100




```python
class Person:
    def __init__(self, name, age):
        self._name = name
        self._age = age
    @property    
    def name(self):
        return self._name
    
    def rename(self, new_name):
        self._name = new_name
```


```python
p = Person('liu', 24)
p.name
```




    'liu'