学习笔记（10):第二章 程序设计与数据结构-看Python如何灵活应用经典设计模式 4...

立即学习:https://edu.csdn.net/course/play/25504/304708?utm_source=blogtoedu

# python中函数即是变量
# abs(-10)函数调用，abs是函数本身
print(abs(-10))

# 函数同样可以赋值给变量
f=abs
print(f(-10))

# abs也可以被覆盖掉
# abs=10
# abs(-10)

# 函数可以作为参数传递
def add(x,y,f):
    return f(x)+f(y)

print(add(-5,6,abs))

'''
    map函数
'''
l = [1,2,3,4,5,6,7,8,9]

def f(x):
    return x*x

m = map(f, l)
print(m) #结果以迭代器对象返回
# 迭代器只能访问一遍
# print(list(m))
# for n in m:
#     print(n)

print(next(m))
print(next(m))
print(next(m))

# 将l列表中的每个int转换成字符串
l=[1,2,3,4,5,6,7,8,9]
print(list(map(str,l)))

'''
    reduce
'''

l=[1,2,3,4,5,6,7]
from functools import reduce
def f(x,y):
    return x*10+y

print(reduce(f, l))

# 实现str2int
def char2int(x):
    digits = {'0':0, '1':1, '2':2, '3':3, '4':4, '5':5, '6':6, '7':7, '8':8, '9':9}
    return digits[x]

print(reduce(f, map(char2int, '23556')))

'''
    匿名函数，在函数中定义函数
'''
DIGITS = {'0':0, '1':1, '2':2, '3':3, '4':4, '5':5, '6':6, '7':7, '8':8, '9':9}
def str2int(s):
    def f(x,y):
        return x*10 +y
    def char2int(x):
        return DIGITS[x]
    return reduce(f, map(char2int, s))

print(str2int('123556'))

# lambda表达式
def str2int(s):
    def char2num(s):
        return DIGITS[s]
    return reduce(lambda x,y:x*10+y,map(char2num,s))

print(str2int('2432546567'))

'''
    装饰器Decorator
'''
import datetime

# 装饰器 以一个函数作为参数，并返回一个函数
def log(f):
    def write_log(*args,**kw):
        with open('./a.txt','w') as f1:
            f1.write(f.__name__)
            print('写入日志成功，函数名字是：%s' % f.__name__)
            return f(*args,**kw)
    return write_log

def now():
    print(datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S'))
now()


# 调用方式一
# ff = log(now)
# ff()
# print(ff.__name__)

# 调用方式二
@log
def now():
    print(datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S'))
now()

'''
    python内置的装饰器 @property @setter
'''
# 加上装饰器，方法变属性
class Student(object):
    def __init__(self, score):
        self.__score = score
    def get_grade(self):
        if self.__score >= 90:
            return 'A'
        elif self.__score >=60:
            return 'B'
        else:
            return 'C'

    @property # 在读函数前加上property，读函数变成属性访问
    def score(self):
        return self.__score
    @score.setter # 在写函数前加上setter，写函数变成属性访问
    def score(self, score):
        if 0<=score<=100:
            self.__score = score
        else:
            raise ValueError("不符合规范的输入")

stu1=Student(56)
print(stu1.score)
stu1.score = 78
print(stu1.score)

def normalize(name):
    s1=name[0].upper()
    s2=name[1:].lower()
    return s1+s2

L1=['MIKE','asfdg','SADAGF']
L2=list(map(normalize,L1))
print(L2)