day4-递归以及其他小练习

#函数自己调用自己就是递归
def test():
    print("递归")
    test()
test()

def test1():
    num=input("请输入").strip()
    if num%2==0:
        return num
    test1()
test1()

def is_float(s):
    s=str(s)
    if s.count('.')==1:
        left,rigth=s.split('.')
        if left.isdigit() and rigth.isdigit():
            return True
        elif left.startswith('-') and left.count('-')==1 and left[1:].isdigit()and rigth.isdigit():
            return True
    return False
result=is_float('-0.10')
print(result)

#函数不调用就不会执行
money=500
def test(consume):
    return money-consume
def test1(money):
    return test(money)+money
money=test1(money)
print(money)

a=100#全局变量
def test2():
   # global a
    a=1#局部变量，如果要定义全局变量，global a
    print(a)
test2()
print(a)

def test3():
    c=a+5
    return c
res=test3()
print(res)

def test_1():
    l=[]
    for i in range(50):
        if i%2==0:
            l.append(i)
    return l
print(test_1())

def replace(scr,old,new):
    if old in scr:
       print(new.join(scr.split(old)))
       return new.join(scr.split(old))

    else:
        return scr
replace('123asd123dfg12','123','XXX')