if_test.py

strings=['xxaa','xuo','fwefxxx','woeuxxfei']
print(strings)
#替换方法1
for string in strings:
    if 'xx' in string:
        index=strings.index(string)
        strings[index]=''
print(strings)
strings=['xxaa','xuo','fwefxxx','woeuxxfei']
for index,string in enumerate(strings):
    if 'xx' in string:
        strings[index]=strings[index].replace('xx','')
print(strings)
print("over")

for x in range(1,5):
    print (x)
    if x == 3: break
else:
    print("in")#只有当break不被调用时执行

a=3
if a==1:
    print('a')
elif a==2:
    print('b')
else:
    print('else')