Python NameError，变量“未定义”
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Python NameError, variable 'not defined'
提问by Kaos
the error it returns is:
它返回的错误是：
NameError: name 'lives' is not defined
I know the code isn't as efficient as possible, this is one of my first projects, however whatever i try to do this error pops up, I've tried making a global for it but that didn't help. I would really appreciate some help with this, thanks!
我知道代码不是尽可能高效，这是我的第一个项目之一，但是无论我尝试做什么都会弹出这个错误，我已经尝试为它创建一个全局但没有帮助。我真的很感激这方面的帮助，谢谢！
import random
import time
def main():
global guess,rand_num
win = False
rand_num = 45
lives = 10
while lives > 0 and win == False:
guess = int(input("Guess a number!"))
compare()
print("Well done!")
time.sleep(3)
def compare():
global lives,win
if guess == rand_num:
print("You guessed correct!")
win = True
elif guess > rand_num:
print ("Guess lower!")
lives = lives - 1
else:
print ("Guess higher!")
lives = lives - 1
def repeat():
replay = input("would you like to play again? Y/N")
if replay == "Y":
print("enjoy!")
main()
elif replay == "N":
"Goodbye then, hope you enjoyed!"
time.sleep(3)
os._exit
else:
print("please enter Y or N")
repeat()
main()
repeat()
EDIT: putting global lives inside main() returns the error:
编辑：将全局生命放入 main() 返回错误：
UnboundLocalError: local variable 'lives' referenced before assignment
回答by Carl 'Subzidion' Hiltbrunner
You need to define the variable "lives" outside of the function main, then any function where you want to reference that global variable you say "global lives." When you are in a function and assign a value to a variable, it assumes it is in the local scope. using "global lives" tells that function to look to the global scope as the reference of lives.
您需要在函数 main 之外定义变量“lives”，然后在要引用该全局变量的任何函数中定义“global life”。当您在函数中并为变量赋值时，它假定它在局部作用域中。使用“全局生命”告诉该函数将全局范围视为生命的参考。
import random
import time
lives = 10
win = False
guess = 0
rand_num = 45
def main():
global guess, rand_num, lives, win
win = False
rand_num = 45
lives = 10
while lives > 0 and win == False:
guess = int(input("Guess a number!"))
compare()
print("Well done!")
time.sleep(3)
def compare():
global guess, rand_num, lives, win
if guess == rand_num:
print("You guessed correct!")
win = True
elif guess > rand_num:
print ("Guess lower!")
lives = lives - 1
else:
print ("Guess higher!")
lives = lives - 1
def repeat():
replay = input("would you like to play again? Y/N")
if replay == "Y":
print("enjoy!")
main()
elif replay == "N":
"Goodbye then, hope you enjoyed!"
time.sleep(3)
os._exit
else:
print("please enter Y or N")
repeat()
main()
repeat()
回答by chepner
You didn't declare livesto be global inside main(), so it is local to that function.
您没有lives在 内部声明为 global main()，因此它对该函数是本地的。
def main():
global guess, rand_num, lives
...
回答by Teemo
When you declare it inside function they are only available in that function scope, so declare global variables outside functions and code will work fine.
当您在函数内部声明它时，它们仅在该函数范围内可用，因此在函数和代码之外声明全局变量将正常工作。
import random
import time
guess = None
random_num = None
lives = 3
win = False
def main():
global guess,rand_num
win = False
rand_num = 45
lives = 10
while lives > 0 and win == False:
guess = int(input("Guess a number!"))
compare()
print("Well done!")
time.sleep(3)
def compare():
global lives,win
if guess == rand_num:
print("You guessed correct!")
win = True
elif guess > rand_num:
print ("Guess lower!")
lives = lives - 1
else:
print ("Guess higher!")
lives = lives - 1
def repeat():
replay = input("would you like to play again? Y/N")
if replay == "Y":
print("enjoy!")
main()
elif replay == "N":
"Goodbye then, hope you enjoyed!"
time.sleep(3)
os._exit
else:
print("please enter Y or N")
repeat()
main()
repeat()
And now this works fine. For more info about gloval vs local variables you can read: http://www.python-course.eu/global_vs_local_variables.php
现在这工作正常。有关全局变量与局部变量的更多信息，您可以阅读：http://www.python-course.eu/global_vs_local_variables.php
