(Python) 验证循环未按预期更新变量
(Python) Validation loop not updating variable as expected
我刚开始学习 Python，只读了 6 章 从 Python 开始，第 4 版。我正在尝试编写一个非常简化的二十一点游戏，但我目前的问题在于如果用户想要尝试重复游戏（即“你想再玩一次吗？”）。当我输入无效的选择时，正确的验证消息出现。但是当再次提示问题时，repeat 变量没有用新输入更新，程序只是终止，即使用户选择再次播放。我做错了什么？我正在附加整个程序如下：
# Import the random functionality
import random
# A nifty welcome message
print("Welcome to my Black Jack program! Let's play!\n")
# Define the function for dealing individual cards
def deal_card():
# Because a deck of cards has face cards and aces, we must assign numerical values to these cards.
Jack = 10
Queen = 10
King = 10
Ace = 1
# We make a range from which the random.randrange can choose cards.
cards = [Ace, 2, 3, 4, 5, 6, 7, 8, 9, 10, Jack, Queen, King]
# Another variable to define what is being selected.
drawn_card = cards[random.randrange(1, 13)]
# The return function stores this data until it is recalled later.
return drawn_card
# This function gives us the user's card value.
def get_player_score():
# The player is dealt two cards, so the deal_card function is called twice.
first_player_card = deal_card()
second_player_card = deal_card()
# The value is calculated by adding the two cards.
sum_player_cards = first_player_card + second_player_card
print ("Your card total is: ", sum_player_cards, ".", sep="")
# This primes the feedback loop of "hitting" and "staying"
choice = int(input("\nWould you like to hit or stay?\nEnter 1 for 'hit' or 2 for 'stay'. "))
# The player should only have this choice when their card value is not over 21.
while sum_player_cards < 21:
if choice == 1:
new_card = deal_card()
sum_player_cards = sum_player_cards + new_card
print ("\nYour new total is: ", sum_player_cards, ".", sep="")
# Again, if the card value is over 21, their turn is over.
if sum_player_cards < 21:
choice = int(input("\nWould you like to to hit or stay? Enter 1 for 'hit' or 2 for 'stay'. "))
# If the card value is over 21, then the function ends.
elif choice == 2:
return sum_player_cards
# Validation check.
else:
print("\nPlease choose 'hit' or 'stay'.")
choice = int(input("\nAgain, would you like to hit or stay? Enter 1 for 'hit' or 2 for 'stay'. "))
# If somehow the card value is over 21 at this point, the function ends.
if sum_player_cards >= 21:
return sum_player_cards
# Now we determine the dealer's score in much the same way.
def get_dealer_score():
# Two cards are drawn for the dealer.
first_dealer_card = deal_card()
second_dealer_card = deal_card()
sum_dealer_cards = int(first_dealer_card + second_dealer_card)
# Here, we must automatically decide for the dealer that if their card value is below 17, they must draw another card.
while sum_dealer_cards <= 16:
another_dealer_card = deal_card()
sum_dealer_cards = sum_dealer_cards + another_dealer_card
# The previous loop stops when their card value is above 16.
if sum_dealer_cards > 16:
print("\nThe dealer's card total is: ", sum_dealer_cards, ".", sep="")
# The value for the dealer cards is now stored.
return sum_dealer_cards
# The main function controls the other major functions and determines if the program is repeated.
def main():
# These new variables allow for the player and dealer card values to be compared.
player_score = get_player_score()
dealer_score = get_dealer_score()
# Now we must define the various end game conditions.
if player_score > dealer_score and player_score <= 21:
print("\nYou win!")
elif dealer_score > player_score and dealer_score <= 21:
print("\nThe dealer wins!")
elif dealer_score <= 21 and player_score > 21:
print("\nYou've gone bust! Dealer wins!")
elif dealer_score > 21 and player_score <= 21:
print("\nThe dealer busts! You win!")
elif dealer_score > 21 and player_score > 21:
print("\nYou've both gone bust! Nobody wins!")
elif player_score == dealer_score:
print("\nPush! Nobody wins!")
# Prime the variable in order to replay the game.
repeat = int(input("\nDo you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
# This repeats the entire main function, which controls the rest of the program.
main()
elif repeat == 2:
# Here we end the program.
return repeat
else:
# Validation check
print("Please enter a valid choice.")
repeat = int(input("Again, do you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
# And this short line activates the rest of the program.
main()
问题出在这部分代码的 else 条件下。
repeat = int(input("\nDo you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
# This repeats the entire main function, which controls the rest of the program.
main()
elif repeat == 2:
# Here we end the program.
return repeat
else:
# Validation check
print("Please enter a valid choice.")
repeat = int(input("Again, do you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
您在更新 repeat 变量后没有做任何事情，这就是程序刚刚终止的原因。您可能希望从 main 函数中删除该代码，并在调用 main() 之后添加它，如下所示。
main()
while True:
repeat = int(input("\nDo you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
main()
elif repeat == 2:
break
else:
print("Please enter a valid choice.")
并相应地修改您的程序。
如果您想重复某些内容，请使用循环。另外，要重复整个程序，不要递归调用 main，而是将其主体包裹在一个循环中。例如，您可以这样编写代码：
def main():
while True: # infinite loop, programm will repeat until return (or break) is called
# stuff
while True: # another infinite loop
repeat = int(input("Again, do you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
break # exit input loop, but not main loop, programm starts over
elif repeat == 2:
return # exit main
else:
print("Please enter a valid choice.") # invalid input, input loop keeps going
我刚开始学习 Python，只读了 6 章 从 Python 开始，第 4 版。我正在尝试编写一个非常简化的二十一点游戏，但我目前的问题在于如果用户想要尝试重复游戏（即“你想再玩一次吗？”）。当我输入无效的选择时，正确的验证消息出现。但是当再次提示问题时，repeat 变量没有用新输入更新，程序只是终止，即使用户选择再次播放。我做错了什么？我正在附加整个程序如下：
# Import the random functionality
import random
# A nifty welcome message
print("Welcome to my Black Jack program! Let's play!\n")
# Define the function for dealing individual cards
def deal_card():
# Because a deck of cards has face cards and aces, we must assign numerical values to these cards.
Jack = 10
Queen = 10
King = 10
Ace = 1
# We make a range from which the random.randrange can choose cards.
cards = [Ace, 2, 3, 4, 5, 6, 7, 8, 9, 10, Jack, Queen, King]
# Another variable to define what is being selected.
drawn_card = cards[random.randrange(1, 13)]
# The return function stores this data until it is recalled later.
return drawn_card
# This function gives us the user's card value.
def get_player_score():
# The player is dealt two cards, so the deal_card function is called twice.
first_player_card = deal_card()
second_player_card = deal_card()
# The value is calculated by adding the two cards.
sum_player_cards = first_player_card + second_player_card
print ("Your card total is: ", sum_player_cards, ".", sep="")
# This primes the feedback loop of "hitting" and "staying"
choice = int(input("\nWould you like to hit or stay?\nEnter 1 for 'hit' or 2 for 'stay'. "))
# The player should only have this choice when their card value is not over 21.
while sum_player_cards < 21:
if choice == 1:
new_card = deal_card()
sum_player_cards = sum_player_cards + new_card
print ("\nYour new total is: ", sum_player_cards, ".", sep="")
# Again, if the card value is over 21, their turn is over.
if sum_player_cards < 21:
choice = int(input("\nWould you like to to hit or stay? Enter 1 for 'hit' or 2 for 'stay'. "))
# If the card value is over 21, then the function ends.
elif choice == 2:
return sum_player_cards
# Validation check.
else:
print("\nPlease choose 'hit' or 'stay'.")
choice = int(input("\nAgain, would you like to hit or stay? Enter 1 for 'hit' or 2 for 'stay'. "))
# If somehow the card value is over 21 at this point, the function ends.
if sum_player_cards >= 21:
return sum_player_cards
# Now we determine the dealer's score in much the same way.
def get_dealer_score():
# Two cards are drawn for the dealer.
first_dealer_card = deal_card()
second_dealer_card = deal_card()
sum_dealer_cards = int(first_dealer_card + second_dealer_card)
# Here, we must automatically decide for the dealer that if their card value is below 17, they must draw another card.
while sum_dealer_cards <= 16:
another_dealer_card = deal_card()
sum_dealer_cards = sum_dealer_cards + another_dealer_card
# The previous loop stops when their card value is above 16.
if sum_dealer_cards > 16:
print("\nThe dealer's card total is: ", sum_dealer_cards, ".", sep="")
# The value for the dealer cards is now stored.
return sum_dealer_cards
# The main function controls the other major functions and determines if the program is repeated.
def main():
# These new variables allow for the player and dealer card values to be compared.
player_score = get_player_score()
dealer_score = get_dealer_score()
# Now we must define the various end game conditions.
if player_score > dealer_score and player_score <= 21:
print("\nYou win!")
elif dealer_score > player_score and dealer_score <= 21:
print("\nThe dealer wins!")
elif dealer_score <= 21 and player_score > 21:
print("\nYou've gone bust! Dealer wins!")
elif dealer_score > 21 and player_score <= 21:
print("\nThe dealer busts! You win!")
elif dealer_score > 21 and player_score > 21:
print("\nYou've both gone bust! Nobody wins!")
elif player_score == dealer_score:
print("\nPush! Nobody wins!")
# Prime the variable in order to replay the game.
repeat = int(input("\nDo you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
# This repeats the entire main function, which controls the rest of the program.
main()
elif repeat == 2:
# Here we end the program.
return repeat
else:
# Validation check
print("Please enter a valid choice.")
repeat = int(input("Again, do you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
# And this short line activates the rest of the program.
main()
问题出在这部分代码的 else 条件下。
repeat = int(input("\nDo you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
# This repeats the entire main function, which controls the rest of the program.
main()
elif repeat == 2:
# Here we end the program.
return repeat
else:
# Validation check
print("Please enter a valid choice.")
repeat = int(input("Again, do you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
您在更新 repeat 变量后没有做任何事情，这就是程序刚刚终止的原因。您可能希望从 main 函数中删除该代码，并在调用 main() 之后添加它，如下所示。
main()
while True:
repeat = int(input("\nDo you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
main()
elif repeat == 2:
break
else:
print("Please enter a valid choice.")
并相应地修改您的程序。
如果您想重复某些内容，请使用循环。另外，要重复整个程序，不要递归调用 main，而是将其主体包裹在一个循环中。例如，您可以这样编写代码：
def main():
while True: # infinite loop, programm will repeat until return (or break) is called
# stuff
while True: # another infinite loop
repeat = int(input("Again, do you want to play again?\nIf 'Yes', enter 1. If 'No', enter 2. "))
if repeat == 1:
break # exit input loop, but not main loop, programm starts over
elif repeat == 2:
return # exit main
else:
print("Please enter a valid choice.") # invalid input, input loop keeps going