初学Python-第二章练习题

2-8 循环和操作符。创建一个包含五个固定数值的列表和元组，输出他们的和。然后修改代码为接受用户的输入数值。

while循环：

!/usr/bin/python

a = []

b = 0

c = 0

while b < 5:

a.append(int(raw_input(‘Input something: ‘)))

c = c + a

b = b + 1

print c

for循环：

!/usr/bin/python

a = []

b = 0

c = 0

for x in range(5):

a.append(int(raw_input(‘Input something: ‘)))

c = c + a[b]

b = b + 1

print c

2-9 循环和操作符。创建一个包含五个固定数值的列表和元组，输出他们的平均值。

PS：重点在除法传统的除法 / 对整型除法会舍去小数点部分，而地板除法 // 不管什么类型的作数都会舍去小数点部分，所以需要使用浮点型进行计算，除非引用真正的除法（from [b]future import division）

!/usr/bin/python

a = []

b = 0

c = 0

while b < 5:

a.append(float(raw_input(‘Input something: ‘)))

c = c + a[b]

b = b + 1

print c

2-10 带循环和条件判断。

!/usr/bin/python

while True:

num = int(raw_input(‘Please input a number between 1 and 100: ‘))

if 1 <= num <= 100:

print ‘Yes,you are right’

break

else:

print “Input number is not between 1 and 100”

continue

2-11 带文本的菜单，菜单项如下：（1）取五个数的和，（2）取五个数的平均值，（x）退出。

!/usr/bin/python

！-- coding:utf-8 --

while True:

print '(1) 取五个数到和'
print '(2) 取五个数到平均值'
print '(x) 退出'

select = raw_input('What want you to do: ')

if select == '1':
a = []
b = 0
c = 0
while b < 5:
a.append(int(raw_input('Input number: ')))
c = c + a[b]
b = b + 1
print c
elif select == '2':
a = []
b = 0
c = 0
while b < 5:
a.append(float(raw_input('Input something: ')))
c = c + a[b]
b = b + 1
print c / len(a)
elif select == 'x':
break
else:
continue