函数（五）-内置函数

内置函数

1 abs():取绝对值

print(abs(-10))  # 10
print(abs(10))  # 10

2 max,min()取最大最小值

# 参数形式1：max(ars1,args2...)
#  全部数字
# print(max(1,23,5,34,8,987,9,3,3,32,))  # 987

# 字母
# print(max('v','w','wrq','hh','sw'))  # wrq

# 参数形式2：max(iterable)
# print(max([12,4,5,7,2,6,97]))  # 97
# print(max([12,4,5,7,2,6,97],23,5,6,12,999))  # 错误


### 指定规则查找最大值，key参数必须为函数
# 按照绝对值大小
# print(max([1,4,99,-100,43],key=abs))  # -100


#
lst = [
    {"name":'wer','price':100},
    {"name":'qq','price':70},
    {"name":'yy','price':99},
]

# 按照name字母顺序
def func(d):
    return d['name']

# 按照价钱排序
def func2(d):
    return d['price']

print(max(lst,key=func))
print(max(lst,key=func2))

3 map

# 将lst转化为[1,4,9]
lst = [1,2,3]

# 方法1
# l2= []
# for i in lst:
#     l2.append(i*i)

# 法2：列表推导式
# lst2 = [i**2 for i in lst]

# 法3：map
# def f(x):
#     return x*x
#
# res = map(f,lst)
# res2 = map(f,lst)
# for i in res2:
#     print(i)  # 1  4  9
#
# lst2 = list(res)  # [1,4,9]
# print(lst2)

4 filter

# 练习:过滤出列表中的所有奇数
l = list(range(1,11))
# 推导式
l2 = [i for i in l if i%2 == 1]


# filter
def f2(x):
    if x % 2 == 1:
        return True
    else:
        return False

5 zip

# for i in zip([1,2,3,4],[4,5,6,],[7,8,9]):   # (1,4,7)
#     print(i)

# print(list(zip([1,2,3],[4,5,6,],[7,8,9])))


# 练习：现有两个元组('a','b'),('c','d')，请生成[{'a':'c'},{'b':'d'}]格式.

# 法1
# l3 = []
# for i in zip(('a','b'),('c','d')):
#     l3.append({i[0]:i[1]})
# print(l3)

# 法2
# l3 = [{i[0]:i[1]} for i in zip(('a','b'),('c','d'))]
# print(l3)