Python之‘’控制流‘’

一、if语句

格式：

i1 = 3
if i1 > 4:
    print('yes you are right')
elif 0 < i1 < 4:
    print('im dont konw')
else:
    print('no you are wrong')

注意if、elif以及else后面的（:）符号，我们通过它告诉Python下面跟着一个语句块。

二、while语句

number = 23
running = True

while running:
    guess = int(input('enter an integer:'))

    if guess == number:
        print('congratulations,you guessed it')
        running = False
    elif guess < number:
        print('no,it is a little lower than that')
    else:
        print('no,it is a little higher than that ')
else:
    print('the while loop is over')

print('done')

输出结果：

enter an integer:22
no,it is a little lower than that
enter an integer:24
no,it is a little higher than that
enter an integer:23
congratulations,you guessed it
the while loop is over
done

注意：在Python2.x版本中输入使用的是raw_input而在Python3.x版本中输入使用的是input。并且后面都要跟冒号。

三、for循环

格式：for...in

for i in range(1,5):
    print(i)
else:
    print('the loop is over')

结果：
C:Python36python.exe C:/Users/蔡瑞/7.py
1
2
3
4
the loop is over

Process finished with exit code 0

注意：range(1,5)只是输出1-4没有5。还有，else部分是可选的，如果包含else，它总是在for循环结束后执行一次，除非遇到break语句。

for循环在这个范围内递归，这就相当于把序列中的每个数（或对象）赋值给i，一次一个，然后以每个i的值执行这个程序块。

Programming is fun 

When the work is done

if you wanna make your work also fun:

　　use Python