while循环在Python中持续运行，输入良好或不好？

嗨，这是我的第一个Python代码，与我一起裸露。我正在编写一个代码，要求用户输入一个百分比，并一直询问，直到用户输入可接受的输入。然而当我运行这个时，无论输入什么样的输入，while循环都不会中断。while循环在Python中持续运行，输入良好或不好？

这里是我的代码：

import math 

while True: 
    try: 
     entered = float(raw_input("Please enter the velocity (as a percentage of the speed of light): ")) 
    except ValueError: 
     print("Sorry, an acceptable input was not entered. Try again.") 
     continue 

    if entered > 100: 
     print("Sorry, a velocity greater than the speed of light cannot be used. Try again.") 
     continue 
    elif entered <= 0: 
     print("Sorry, a percent cannot be negative. Try again.") 
     continue 
    else: 
     #the percent entered is valid, break out of while loop 
     break 

print("Ship is traveling at ", entered, "% the speed of light.") 
print(" ") 

speedOfLight = 299792458       #speed of light constant 
percentage = entered/100      #turn entered percent into decimal 
speed = speedOfLight * percentage    #actual speed (in m/s)   
denominator = math.sqrt(1 - (percentage ** 2)) #denominator of factor equation 
factor = 1/denominator      #solve for given factor equation 

shipWeight = 70000 * factor      #given ship weight * factor 
alphaCentauri = 4.3/factor      # given times divided by the factor 
barnardsStar = 6.0/factor 
betelgeuse = 309 /factor 
andromeda = 2000000/factor 

print("At this speed: ") 
print(" Weight of the shuttle is ", shipWeight) 
print(" Perceived time to travel to Alpha Centauri is ", alphaCentauri, " years.") 
print(" Perceived time to travel to Barnard's Star is ", barnardsStar, " years.") 
print(" Perceived time to travel to Betelgeuse is ", betelgeuse, " years.") 
print(" Perceived time to travel to Andromeda Galaxy is ", andromeda, " years.")

来源

2016-03-31 Clarisa

请花时间来修复缩进，使我们可以帮助你的作品如下。 – Dzhao

你压痕有点靠不住，代码永远不会到达break声明，因为你在continue之前的循环。幸运的是，你可以使用和else关键字，使其工作：

while True: 
    try: 
     entered = float(raw_input("Please enter the velocity (as a percentage of the speed of light): ")) 
    except ValueError: 
     print("Sorry, an acceptable input was not entered. Try again.") 
     continue 
    else: # no exception 
     if entered > 100: 
      print("Sorry, a velocity greater than the speed of light cannot be used. Try again.") 
      continue 
     elif entered <= 0: 
      print("Sorry, a percent cannot be negative. Try again.") 
      continue 
     else: 
      #the percent entered is valid, break out of while loop 
      break

来源

2016-03-31 03:05:54 Ben

是啊我的坏我总是弄乱缩进当我在这个网站上输入代码。但是，谢谢你，它像一个魅力工作！ – Clarisa

@Clarisa一旦你习惯了缩进，python就是其中最优秀的语言之一。好好享受：） – Ben

您检查您的except内部数据的输入。除非投射到float产生ValueError，否则你将永远不会进入你的场地。

你只是想移动except块之外的条件，所以你可以检查经过float铸造的数据：

while True: 
    try: 
     entered = float(input("Please enter the velocity (as a percentage of the speed of light): ")) 
    except ValueError: 
     print("Sorry, an acceptable input was not entered. Try again.") 
     continue 

    if entered > 100: 
     print("Sorry, a velocity greater than the speed of light cannot be used. Try again.") 
     continue 
    elif entered <= 0: 
     print("Sorry, a percent cannot be negative. Try again.") 
     continue 
    else: 
     #the percent entered is valid, break out of while loop 
     break

来源

2016-03-31 03:04:38 idjaw

我认为（希望）编辑搞砸了，因为它是无效的语法写在问题 – TinyTheBrontosaurus

你甚至都不需要继续/休息，以使这项工作。您还需要“导入数学”，一旦最终摆脱while循环，这将很重要。

你需要做的是观察凹痕。 try/except的位置不正确 - 如果这反映了代码实际上是如何编写的，那将会说明你永远不会停止while循环。

按你们的要求，只有缩进修复和“进口数学”

import math 

valid = False 

while not valid: 
    try: 
      entered = float(raw_input("Please enter the velocity (as a percentage of the speed of light): ")) 
    except ValueError: 
      print("Sorry, an acceptable input was not entered. Try again.") 
      continue 

    if entered > 100: 
     print("Sorry, a velocity greater than the speed of light cannot be used. Try again.") 
    elif entered <= 0: 
     print("Sorry, a percent cannot be negative. Try again.") 
    else: 
     #the percent entered is valid, break out of while loop 
      valid = True 

print("Ship is traveling at ", entered, "% the speed of light.") 
print(" ") 

speedOfLight = 299792458       #speed of light constant 
percentage = entered/100      #turn entered percent into decimal 
speed = speedOfLight * percentage    #actual speed (in m/s)   
denominator = math.sqrt(1 - (percentage ** 2)) #denominator of factor equation 
factor = 1/denominator      #solve for given factor equation 

shipWeight = 70000 * factor      #given ship weight * factor 
alphaCentauri = 4.3/factor      # given times divided by the factor 
barnardsStar = 6.0/factor 
betelgeuse = 309 /factor 
andromeda = 2000000/factor 

print("At this speed: ") 
print(" Weight of the shuttle is ", shipWeight) 
print(" Perceived time to travel to Alpha Centauri is ", alphaCentauri, " years.") 
print(" Perceived time to travel to Barnard's Star is ", barnardsStar, " years.") 
print(" Perceived time to travel to Betelgeuse is ", betelgeuse, " years.") 
print(" Perceived time to travel to Andromeda Galaxy is ", andromeda, " years.")

来源

2016-03-31 03:14:51 Lost

while循环在Python中持续运行，输入良好或不好？

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