Python中的while循环和范围数

Question

正在为学校编写代码，我需要将其修改为仅允许用户输入 0 到 20o 的范围。这是到目前为止的代码。每次我尝试放置一个 while 循环时，它都不起作用，我仍然可以输入任何高于 200 的值。任何帮助将不胜感激。

import turtle  #allows access to a collection of Python functions that make it possible to draw

Jane = turtle.Turtle()  #creates a "turtle" to do our drawing for us; we will call the turtle Jane

# the next four lines get input from the user so we know how tall to make the bars in the graph

bar1 = int(input("What is the height of the first bar?" ))

bar2 = int(input("What is the height of the second bar?" ))

bar3 = int(input("What is the height of the third bar?" ))
  
bar4 = int(input("What is the height of the fourth bar? "))
 
#the turtle always starts out facing left; the next line rotates it so it faces up

Jane.left(90)

#next we will create a function that will draw one bar of the bar graph

#the function requires us to pass the height of the bar into it

def bar(height):
    
    #Jane will make a line that is as long as the height that the user inputted
    
    Jane.forward(height)
    
    #now we will turn Jane to the left to make the top of the bar
    
    Jane.left(90)
    
    #now Jane needs to more forward to draw the top of the bar
    
    Jane.forward(20)
    
    #now Jane needs to turn left 
     
    Jane.left(90)
    
    #now Jane needs to draw a line that is as long as the height
    
    Jane.forward(height)
    
    #now Jane needs to rotate 180 degrees to be ready for the next bar
    
    Jane.right(180)

#now we will call the function four times--one for each bar. Notice that

#we will go in the order 4-3-2-1, since the bars will be drawn from right to left

bar(bar4)

bar(bar3)

bar(bar2)

bar(bar1)

Answer 1

像这样？

def limit_input(prompt):
    while True:
        value = int(input(prompt))
        if value < 200:
            return value
        print( "Please keep your value below 200.")

bar1 = limit_input("What is the height of the first bar?")
bar2 = limit_input("What is the height of the second bar?")
bar3 = limit_input("What is the height of the third bar?")
bar4 = limit_input("What is the height of the fourth bar?")

留给读者的一个练习是添加一个try/except ValueError 子句，以便在用户键入数字以外的内容时进行捕捉。

Answer 2

请看这段代码。我认为您正在寻找这样的代码。

import turtle

Jane = turtle.Turtle()

bars = []
for i in range(4):
    height = 201
    while height > 200:
        height = int(input(f'What is the height of the {i + 1}. bar? (from 1 to 200))'))
    bars.append(height)

Jane.left(90)


def bar(height):
    Jane.forward(height)
    Jane.left(90)
    Jane.forward(20)
    Jane.left(90)
    Jane.forward(height)
    Jane.right(180)


for b in bars:
    bar(b)