python中的while循环不起作用

Question

pointsToAdd = 30
strengthPoints = 0
healthPoints = 0
wisdomPoints= 0
dexterityPoints = 0

while pointsToAdd > 0:
    choice = int(input("Choice(1-4): "))
    if choice == 1:
        pointsToAdd = int(input("How many Strength points would you like to add: "))
        if pointsToAdd < 31 and pointsToAdd > 0 and pointsToAdd - strengthPoints > 0:
            strengthPoints += pointsToAdd
            pointsToAdd -= strengthPoints
            print("You now have",strengthPoints,"strength points")
        elif pointsToAdd > 30:
            print("You cannot add that many!")
        elif pointsToAdd<1:
            print("You cannot add less than one point!")
        elif pointsToAdd - strengthPoints <= 0:
            print("You only have",pointsToAdd,"points!")
        else:
            print("We are sorry, but an error has occurred")

I am trying to make it so that the user can enter points for any of the four categories, but has no more than 30 points to expend(I have not yet written the code for the health, wisdom or dexterity points). Why when i run the program does the loop only run again if you choose to add a number of points between 1-30? If the user enters the points they want to allocate towards strengthPoints using numbers not between 1-30, the loop will run the associated if statement, but will not run through the loop again, why is this the case?

Answer 1

you are using the same variable for two different purposes pointsToAdd . You have it as the total points to assign, and what was selected by the user to add to a stat. Once you stomp the total points to assign with the users choice, you then add it to the 0 strength and subtract it from your user entered value, setting it to zero. Using to separate variables like below will fix it.

totalPointsToAdd = 30
strengthPoints = 0
healthPoints = 0
wisdomPoints= 0
dexterityPoints = 0

while totalPointsToAdd > 0:
    choice = int(input("Choice(1-4): "))
    if choice == 1:
        pointsToAdd = int(input("How many Strength points would you like to add: "))
    if pointsToAdd < 31 and pointsToAdd > 0 and pointsToAdd - strengthPoints > 0:
        strengthPoints += pointsToAdd
        totalPointsToAdd -= pointsToAdd
        print("You now have",strengthPoints,"strength points")

Answer 2

You do

pointsToAdd = 30

Then in the loop

pointsToAdd = int(input("How many Strength points would you like to add: "))

Then in the test

# Here pointsToAdd is not 30, but the value inputed by the user
strengthPoints += pointsToAdd
# Here strengthPoints == pointsToAdd == the value from the input
pointsToAdd -= strengthPoints
# Here pointsToAdd == 0

This results in pointsToAdd == 0 after than.

You need to use another variable for the input of your user.

Answer 3

As other pointed out you are overwriting the same variable pointsToAdd . I also consider that you can cut down your conditions to two:

pointsToAdd = 30
strengthPoints = 0

while pointsToAdd:
    print ('You have', pointsToAdd, 'available points.')
    choice = int(input("Choice(1-4): "))
    if choice == 1:
        toBeAdded = int(input("How many Strength points would you like to add: "))
        if toBeAdded < 1: # Can't assign negative or null values
            print("You cannot add less than one point!")
            continue
        if toBeAdded > pointsToAdd: # Don't have enough points to spend
            print("You only have", pointsToAdd, "available points!")
            continue
        strengthPoints += toBeAdded
        pointsToAdd -= toBeAdded
        print("You now have", strengthPoints, "strength points")

Answer 4

In Python 2.x use: raw_input In Python 3.x use: input

If you want compatibility between Python 2.x and 3.x, you can use:

try:
    input = raw_input
except NameError:
    pass