python 函数

#函数
def welcome():
    print('欢迎你')
welcome()

def write_file(file_name,cotent):
    f = open(file_name,'a+',encoding='UTF-8')
    f.write(cotent)
    f.seek(0)
    x = f.read()
    print(x)
    f.close()

write_file('a.txt','今天天气好晴朗')

def op_file(file,content=None):# file为必填参数，content为可选参数
    f = open(file,'a+',encoding='UTF-8')
    if content:
        f.write(content)
    else:
        f.seek(0)
        return f.read()

print(op_file('1.txt'))
print('1.txt','lijun,989098')

def get_user():
    name = 'xiaoming'
    sex = '男'
    return name,sex  #返回多个值时，返回的为元祖，元祖内容无法修改

print(get_user())

#全局变量若需要修改，需要先申明
day = 1
def get_1():
    global day #修改全局变量必须先申明
    day = day + 1
    print(day)
get_1()

l = [1,1,2,3,4,5,6,7]
for i in l:
    if i % 2 != 0:
        l.remove(i)  #在删除了位置0的1时，位置0还是1，就忽略了未循环到
print(l)

l = [1,1,2,3,4,5,6,7]
l2 = [1,1,2,3,4,5,6,7]
for i in l2:
    if i % 2 != 0:
        l.remove(i)  #用l2作循环，删除l，不会跳过任意值
print(l)

#因此，循环list时不要删除元素，会导致值未循环