python基础4--控制流

1、if语句

结构：

if condition:

     do something

elif other_condition:

     do something

number = 60
guess = int(input('Enter an integer : '))

if (guess == number):
    # New block starts here
    print('Bingo! you guessed it right.')
    # New block ends here
elif (guess < number):
    # Another block
    print('No, the number is higher than that')
    # You can do whatever you want in a block ...
else:
    print('No, the number is a  lower than that')
    # you must have guessed > number to reach here

print('Done')

 

2、循环语句允许我们执行一个语句或语句组多次，下面是在大多数编程语言中的循环语句的一般形式：

 

3、for语句

for i in range(1, 10):
    print(i)
else:
    print('The for loop is over')

#遍历List
a_list = [1, 3, 5, 7, 9]
for i in a_list:
    print(i)

#遍历Tuple
a_tuple = (1, 3, 5, 7, 9)
for i in a_tuple:
    print(i)

#遍历Dict
a_dict = {'Tom':'111', 'Jerry':'222', 'Cathy':'333'}
for key in a_dict:
    print(key, a_dict[key])

for (key, elem) in a_dict.items():
    print(key, elem)

运行结果：

 

4、while语句

number = 59
guess_flag = False

while (guess_flag == False):
    guess = int(input('Enter an integer : '))
    if guess == number:
        guess_flag = True
    elif guess < number:
        print('No, the number is higher than that, keep guessing')
    else:
        print('No, the number is a  lower than that, keep guessing')
print('Bingo! you guessed it right.')

 

5、break, continue, pass

(1) break 语句：跳出循环

(2) continue 语句：进行下一次循环

(3) pass 语句：什么都不做

number = 59
while True:
    guess = int(input('Enter an integer : '))
    if guess == number:
        break
    if guess < number:
        print('No, the number is higher than that, keep guessing')
        continue
    else:
        print('No, the number is a  lower than that, keep guessing')
        continue

print('Bingo! you guessed it right.')
print('Done')