第 7 章

测试题

输出将是：

Under 20

因为 my_number 小于 20，if 语句中的测试为 true，所以会执行 if 后面的块（这里只有一行代码）。

输出将是：

20 or over

因为 my_number 大于 20，if 语句中的测试为 false，所以 if 后面的块代码不会执行。相反，会执行 else 块中的代码。

要查看一个数是否大于 30 但小于或等于 40，可以使用下面的代码：

if number > 30 and number <= 40:
    print 'The number is between 30 and 40'

你还可以这样做：

if 30 < number <= 40:
    print "The number is between 30 and 40"

要检查字母“Q”是大写还是小写，可以这样做：

if answer == 'Q' or answer == 'q':
    print "you typed a 'Q' "

注意，我们打印的字符串使用了双引号，不过其中的“Q”两边是单引号。如果想知道如何打印引号，可以用另一种引号包围字符串。

动手试一试

下面给出一个答案：

# program to calculate store discount
# 10% off for $10 or less, 20% off for more than $10
item_price = float(raw_input ('enter the price of the item: '))
if item_price <= 10.0:
    discount = item_price * 0.10
else:
    discount = item_price * 0.20
final_price = item_price - discount
print 'You got ', discount, 'off, so your final price was', final_price

这里没有考虑把答案四舍五入为两位小数（美分），也没有显示美元符。

以下给出一种做法：

# program to check age and gender of soccer players
# accept girls who are 10 to 12 years old
gender = raw_input("Are you male or female? ('m' or 'f') ")
if gender == 'f':
    age = int(raw_input('What is your age? '))
    if age >= 10 and age <= 12:
        print 'You can play on the team'
    else:
        print 'You are not the right age.'
else:
    print 'Only girls are allowed on this team.'

以下给出一个答案：

# program to check if you need gas.
# Next station is 200 km away
tank_size = int(raw_input('How big is your tank (liters)? '))
full = int(raw_input ('How full is your tank (eg. 50 for half full)?'))
mileage = int(raw_input ('What is your gas mileage (km per liter)? '))
range = tank_size * (full / 100.0) * mileage
print 'You can go another', range, 'km.'
print 'The next gas station is 200km away.'
if range <= 200:
    print 'GET GAS NOW!'
else:
    print 'You can wait for the next station.'

要增加一个 5 公升的缓冲区，需要把这行代码：

range = tank_size * (full / 100.0) * mileage

改为：

range = (tank_size - 5) * (full / 100.0) * mileage

下面是一个简单的口令程序：

password  = "bigsecret"
guess  = raw_input("Enter your password: ")
if guess == password:
    print "Password correct.  Welcome"
    # put the rest of the code for your program here
else:
    print "Password incorrect.  Goodbye"