函数

# f = open('a.txt','w',encoding='utf-8')
# f.write()
# f.close()

def smile():
    print('哈哈哈')

# smile()
#函数必须调用才会执行
# price = input('请输入价格：')

def is_float(s): #形式参数
    s = str(s)
    if s.count('.') == 1:
        left,right = s.split('.')  #1.74  ['1','74']
        if left.isdigit() and right.isdigit():
            return True
        elif left.startswith('-') and left[1:].isdigit() and right.isdigit():
            return True
    return False



#判断输入的数据是否是一个小数

#1.54
#1、只有一个小数点
#2、小数点左右是整数


#-1.34
#1、只有一个小数点
#2、小数点右边是整数，小数点左边只有一个负号
#负号后面是一个整数





# is_float(1) #实际参数

#1.

#函数的返回值

def calc(a,b):
    result = a+b
    print(result)
    return result

# sum = calc(1,1)


def write_file(file_name,content):
    with open(file_name,'w',encoding='utf-8') as fw:
        fw.write(content)


def read_file(file_name):
    with open(file_name,encoding='utf-8') as fw:
        result = fw.read()
        return result

read_file('users')

#在函数里面定义的变量都是局部变量
#函数里只要遇到return函数立即结束

# username = input('username:')
# res = read_file('users')
#
# if username in res:
#     print('用户名存在！')
# else:
#     print('用户名不存在！')


def more():
    name = 'xiaohei'
    age = 18
    score = 37.5
    return name,age,score

result = more()
print(result)

mingzi,nianling,chengji = more()
print(mingzi)
print(nianling)
print(chengji)

#默认值参数

def register(name,sex='女'):

    print('[%s %s]写入数据库'%(name,sex))

register('贾金菊','男')
register('贾金菊')

#一个函数只实现一个功能，不要写太长的在一个函数里面

import json
def op_file(file_name,content=None):
    if content:
        with open(file_name,'w',encoding='utf-8') as fw:
            fw.write(content)
    else:
        with open(file_name,encoding='utf-8') as fr:
            return fr.read()

def op_file_json(file_name,dic=None):
    if dic:
        with open(file_name,'w',encoding='utf-8') as fw:
            json.dump(dic,fw)
    else:
        with open(file_name,encoding='utf-8') as fr:
            result = json.load(fr)
            return result