U5函数

Unit5 函数

1、函数的参数

1.1、位置参数的使用

def happy_birthday(name,age):
    print("祝" + name + str(age) + "岁生日快乐")
#调用
happy_birthday("小明", 18)

1.2、关键字传参

def happy_birthday(name,age):
    print("祝" + name + str(age) + "岁生日快乐")
#调用
happy_birthday(name = "小明", age = 18)
#happy_birthday(name = "小明", age1 = 18) 错误
happy_birthday("小虎", age = 20)

#传参需要位置传参在前，关键字传参在后
#happy_birthday( name = "小虎", 20)SyntaxError: positional argument follows keyword argument

1.3、默认值参数

def happy_birthday(name = "personname",age = 18):
    print("祝" + name + str(age) + "岁生日快乐")
#调用
happy_birthday("小明", 18)

#TypeError: happy_birthday() missing 2 required positional arguments: 'name' and 'age'
happy_birthday()#默认值
happy_birthday("小明")#位置传参
happy_birthday(age=20)#关键字传参

'''
Traceback (most recent call last):
  File "E:\pythonProject\Learning\Base\Chapter5\_3默认值参数的使用.py", line 11, in <module>
    happy_birthday(19)#报错
    ^^^^^^^^^^^^^^^^^^
  File "E:\pythonProject\Learning\Base\Chapter5\_3默认值参数的使用.py", line 2, in happy_birthday
    print("祝" + name + str(age) + "岁生日快乐")
          ~~~~~~^~~~
TypeError: can only concatenate str (not "int") to str
'''
#happy_birthday(19)#报错


'''
    位置参数在前，关键字参数在后

'''
def fun(a,b = 20):
    pass
# def fun(a = 20 ,b):
#     pass

2、可变参数

#个数可变的位置参数
def fun(*para):
    print(type(para))
    for item in para:
        print(item)

#调用
fun(10,20,30,40)
fun(10)
fun(20,30)
fun([10,20,30,40])#一个参数

#调用时，参数加一颗星，会将列表进行解包
fun(*[10,20,30,40])

#个数可变的关键字参数
def fun2(**kwpara):
    print(type(kwpara))
    for key,value in kwpara.items():
        print(key,"---",value)
#调用
fun2(name = "小明",age = 18, height = 180)

#字典传参需要解包，否则报错
d = {"name":"小明","age":18,"height":180}
#TypeError: fun2() takes 0 positional arguments but 1 was given
#fun2(d)
fun2(**d)

3、返回值

def sum(*para):
    print(type(para))
    sum = 0
    for item in para:
        sum += item
    return sum
print(sum(1, 2, 3, 4, 5))

#列表
s = [1,2,3,4,5]
print(sum(*s))

4、变量的作用域

a = 100 #全局变量
def calc(x,y):
    return a + x + y
print(a)
print(calc(10,20))
print("-"*30)

def calc2(x,y):
    a = 200 #局部遍历
    #局部优先级高
    return a + x + y
print(a)
print(calc2(10,20))
print("-"*30)

def calc3(x,y):
    global s #global全局变量
    s = 300
    return s + x + y
print(calc3(10,20))
print(s)

5、匿名的作用域

def calc(a,b):
    return a + b
print(calc(10,20))

#匿名函数
s = lambda a,b : a + b
print(type(s))#<class 'function'>
#调用
print(s(10,20))
print("*"*30)
lst = [10,20,30,40]
for i in range(len(lst)):
    print(lst[i])
print("*"*30)

for i in range(len(lst)):
    result = lambda x:x[i] #根据索引取值，result类型卫function，x是形式参数
    print(result(lst))
#
student_scores = [
    {"name":"小a","score":90},
    {"name":"小s","score":40},
    {"name":"小d","score":50},
    {"name":"小f","score":60}
]
#对列表排序
student_scores.sort(key=lambda x:x.get("score"),reverse=True)
print(student_scores)

6、递归

#求阶乘
def fac(n):
    if n == 1:
        return 1
    else:
        return n * fac(n - 1)
print(fac(5))

7、斐波那契数列

def fibonacci(n):
    if n == 1 or n == 2:
        return 1
    else:
        return fibonacci(n - 1) + fibonacci(n - 2)
print(fibonacci(10))
print("*"*20)
for i in range(1,10):
    print(fibonacci(i), end="\t")

8、常用内置函数

#bool()
print("非空字符串的布尔值",bool("he"))
print("空字符串的布尔值",bool(""))
print("空列表的布尔值",bool([]))
print("空列表的布尔值",bool(list()))
print("空元组的布尔值",bool(()))
print("空元组的布尔值",bool(tuple()))
print("空集合的布尔值",bool(set()))
print("空字典的布尔值",bool({}))
print("空字典的布尔值",bool(dict()))
print("*"*30)
print("非0数值型的布尔值：", bool(123))
print("整数0的布尔值：", bool(0))
print("浮点数0的布尔值：", bool(0.0))

#将其他类型转成数字类型
lst = [10,20,30]
print(type(lst), lst)
s= str(lst)
print(type(s),s)

#float str -> int
print("*"*30)
print(int(98.5) + int("99"))
#tip
#print(int("98.1"))#ValueError: invalid literal for int() with base 10: '98.1'
print(int("a"))#ValueError: invalid literal for
int() with base 10: 'a'



'''
结果：
    1 0 10
    (3, 1) (3, 1)
    2
    o
    324
    324
    [12, 324, 45, 312, 12.2]
    15
    8
    3
    4
    3.12
    0.0
'''
print(abs(-1),abs(0),abs(10))
print(divmod(13,4),divmod(10,3))
print(max(1,2))
print(max("hello"))
print(max([12,324,45,312,12]))
print(max([12,324,45,312,12.1]))
print(max([12,324,45,312,12.1],[12,324,45,312,12.2]))
#min反之
print(sum([1,2,3,4,5]))
#print(sum(1,2,3,4,5))#TypeError: sum() takes at most 2 arguments (5 given)
#print(sum([1,2,3,4,5],[1,2,3,4,5]))TypeError: can only concatenate list (not "int") to list
print(pow(2,3))

print(round(3.12334234))
print(round(3.82334234))
print(round(3.12334234,2))
print(round(3.12334234,-1))

9、迭代器

9、迭代器

    lst = [1,234,45,345,546,5467,567,56,7567,56687]
    #sort
    asc_lst = sorted(lst)
    desc_lst = sorted(lst,reverse=True)
    print("源列表",lst)
    print("升序",asc_lst)
    print("逆序",desc_lst)

    #reversed 反转
    reversed_lst = reversed(lst)
    print(type(reversed_lst))
    print(list(reversed_lst))

    #zip
    x = ['a','b','c','d','e']
    y = [1,2,3,4]
    zipobj = zip(x,y)
    #会忽略最后一个没对齐的
    print(type(zipobj))
    #strict属性是严格对齐
    #zipobj = zip(x,y,strict=True)
    #print(type(zipobj))
    print((zipobj))


    #enumerate
    enum = enumerate(y , start = 1)
    print(type(enum))
    print(tuple(enum))

    #all
    '''
        all(iterable)
        如果 iterable 的所有元素均为真值（或可迭代对象为空）则返回 True 。 等价于：
    def all(iterable):
        for element in iterable:
            if not element:
                return False
        return True
    '''
    lst2 = [12,"",32]
    print(all(lst2))
    print(all(lst))

    #any
    '''
    any(iterable)
    如果 iterable 的任一元素为真值则返回 True。 如果可迭代对象为空，返回 False。 等价于:
    def any(iterable):
        for element in iterable:
            if element:
                return True
        return False
    '''
    print(any(lst2))
    #next
    '''
    next(iterator, default)
    通过调用 iterator 的 __next__() 方法获取下一个元素。如果迭代器耗尽，则返回给定的 default，如果没有默认值则触发 StopIteration。
    '''
    print(next(zipobj))
    print(next(zipobj))
    print(next(zipobj))
    '''
    filter(function, iterable)
    使用 iterable 中 function 返回真值的元素构造一个迭代器。 iterable 可以是一个序列，一个支持迭代的容器或者一个迭代器。 如果 function 为 None，则会使用标识号函数，也就是说，iterable 中所有具有假值的元素都将被移除。
    '''
    def fun(num):
        return num % 2 == 1
    obj = filter(fun,range(10))
    print(list(obj))

    #map
    def upper(x):
        return x.upper()
    map_lst = ["hello","world","python"]
    obj1 = map[upper, map_lst]
    print(list(obj1))

10、练习

'''
 编写函数实现计算列表中元素最大值
'''
import random
lst = [random.randint(1,101) for i in range(10)]
# for i in range(10):
#     lst.append(random.randint(1,101))
print(lst)
def get_max(lst):
    maxV = lst[0]
    #遍历
    for i in range(1, len(lst)):
        if lst[i] > maxV:
            maxV = lst[i]
    return maxV
print(get_max(lst))


'''
编写函数实现提取指定字符串中的数字并求和
'''
def get_digit(x):
    lst = []
    for item in x:
        if item.isdigit():
            lst.append(int(item))
    return lst,sum(lst)
s = input("请输入一个字符串：")
lst,x = get_digit(s)
print("提取的数字为：", lst)
print("累加和为：", x)


'''
    实现in的功能
'''
def get_find(s,lst):
    for item in lst:
        for i in item:
            if s == i:
                return True
    return False
lst = ["hello","world","python"]
s = "h"
result = get_find(s, lst)
#if..else 的简写
print("存在" if result else "不存在")