如何在函数内保留 运行 总数并允许在函数外访问它？
How to keep a running total inside a function and allow it to be accessed outside of the function?
我想保留 运行 用户摄入的总卡路里数，然后将其插入数据库，同时提供用户摄入卡路里量的反馈。当我在函数外定义 TotalCalories 并将其设置为全局变量（以便它可以在另一个函数内使用）时，我得到错误 UnboundLocalError: local variable 'TotalCalories' referenced before assignment
def FoodSelection(choice):
global CurrentPupil
CurrentPupil = ""
global FoodSelectionWindow
FoodSelectionWindow = Toplevel()
FoodSelectionWindow.configure(bg="black")
DateAdded = datetime.date.today()
TimeTaken = 0
NoFoodOption = 0
#The validation timer starts here:
while TimeTaken < 2:
time.sleep(60)
TimeTaken = TimeTaken +1
#and ends here
class food():
def __init__(self, name = "no name", calories = 0, photo = ""):
self.name = name
self.calories = calories
self.photo = photo
BoiledEggs = food("Boiled Egg", 155, PhotoImage(file="BoiledEgg.gif"))
ScrambledEggs = food("Scrambled Egg", 148, PhotoImage(file="ScrambledEgg.gif"))
FriedEggs = food("Fried Egg", 196, PhotoImage(file="FriedEgg.gif"))
PoachedEggs = food ("Poached Egg", 143, PhotoImage(file="PoachedEgg.gif"))
Toast = food("Toast", 313, PhotoImage(file="Toast.gif"))
Bacon = food("Bacon", 514, PhotoImage(file="Bacon.gif"))
Cereal = food("Cereal", 379, PhotoImage(file="Cereal.gif"))
Porridge = food("Porridge", 68, PhotoImage(file="Cereal.gif"))
NoBreakfast = food("No Breakfast", 0, PhotoImage(file="NoBreakfast.gif"))
def NoFood():
FoodChoices("No Food")
def BoiledEggsFunct():
FoodChoices("Boiled Eggs")
def FriedEggsFunct():
FoodChoices("Fried Eggs")
def ScrambledEggsFunct():
FoodChoices("Scrambled Eggs")
def PoachedEggsFunct():
FoodChoices("Poached Eggs")
def ToastFunct():
FoodChoices("Toast")
def BaconFunct():
FoodChoices("Bacon")
def CerealFunct():
FoodChoices("Cereal")
def PorridgeFunct():
FoodChoices("Porridge")
global TotalCalories
TotalCalories = 0
def FoodChoices(selection):
if selection == "No Food":
TotalCalories = NoBreakfast.calories
elif selection == "Boiled Eggs":
TotalCalories = BoiledEggs.calories + TotalCalories
elif selection == "Fried Eggs":
TotalCalories = FriedEggs.calories + TotalCalories
elif selection == "Scrambled Eggs":
TotalCalories = ScrambledEggs.calories + TotalCalories
elif selection == "Poached Eggs":
TotalCalories = PoachedEggs.calories + TotalCalories
elif selection == "Toast":
TotalCalories = Toast.calories + TotalCalories
elif selection == "Bacon":
TotalCalories = Bacon.calories + TotalCalories
elif selection == "Cereal":
TotalCalories = Cereal.calories + TotalCalories
elif selection == "Porridge":
TotalCalories = Porridge.calories + TotalCalories
if choice == 'chris':
CurrentPupil = "Chris"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"1"]))
elif choice == 'josh':
CurrentPupil = "Josh"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"2"]))
elif choice == 'sam':
CurrentPupil = "Sam"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"3"]))
elif choice == 'daniel':
CurrentPupl = "Daniel"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupillID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil, "4"]))
elif choice == 'jim':
CurrentPupil = "Jim"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"5"]))
elif choice == 'sean':
CurrentPupil = "Sean"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"6"]))
db.commit()
def FeedbackScreen():
FinishWindow = Toplevel()
if TotalCalories > 0 and TotalCalories < 1000:
HealthyLabel = Label(FinishWindow, text = "Congratulations, you are healthy!", font=("Comic Sans MS", 25), fg = "light green",
bg = "black")
HealthyLabel.grid(columnspan=10)
elif TotalCalories > 1000:
UnhealthyLabel = Label(FinishWindow, text = "Try to eat healthier tomorrow. See personalised advice", font=("Comic Sans MS", 25), fg = "yellow",
bg = "black")
UnhealthyLabel.grid(columnspan=10)
elif NoFoodOption == 1:
NoFoodLabel = Label(FinishWindow, text = "Not eating can be harmful to your health. See personalised advice", font=("Comic Sans MS", 25), fg = "red",
bg = "black")
NoFoodLabel.grid(columnspan=10)
else:
Error = Label(FinishWindow, text = "error", font=("Comic Sans MS", 25), fg = "red",
bg = "black")
NoFoodLabel.grid(columnspan=10)
如您所见，我需要在整个代码中的各种函数中使用 TotalCalories，因此我认为通过将其设为全局变量，我可以做到这一点。
有什么建议吗？
这是MCVE你的问题：
global TotalCalories
TotalCalories = 0
def FoodChoices(selection):
if selection == "No Food":
TotalCalories = 100
elif selection == "Boiled Eggs":
TotalCalories = 100 + TotalCalories
FoodChoices("Boiled Eggs")
运行 此代码产生此输出：
$ python test.py
Traceback (most recent call last):
File "test.py", line 13, in <module>
FoodChoices("Boiled Eggs")
File "test.py", line 11, in FoodChoices
TotalCalories = 100 + TotalCalories
UnboundLocalError: local variable 'TotalCalories' referenced before assignment
并在函数中插入 global TotalCalories 使其消失：
def FoodChoices(selection):
global TotalCalories
if selection == "No Food":
TotalCalories = 100
elif selection == "Boiled Eggs":
TotalCalories = 100 + TotalCalories
Python 要求在要使用它的函数中声明一个全局名称，如果您打算重新绑定全局。如果您只是从中读取或改变它，那么您可以在函数中不声明。
您可能没有考虑过替代方案。在 Python 中，出于某些目的，您可以使对象看起来像函数。然后，您可以积累在对象变量中调用函数时收集到的信息。那么在您的情况下， TotalCalories 可能是对象中的变量。诀窍是为对象中的方法使用名称 __call__；变成 'callable'.
class FoodSelection:
def __init__ (self):
self.TotalCalories = 0
def __call__ (self, choice):
if choice == 'potatoes':
print (choice, ''': eat as little as possible!''')
self.TotalCalories += 10000
elif choice == 'salad':
print (choice, ': good choice!')
self.TotalCalories += 0
else:
print (choice, ''': sorry, don't understand that''')
foodSelection = FoodSelection()
foodSelection('potatoes')
print (foodSelection.TotalCalories)
foodSelection('salad')
print (foodSelection.TotalCalories)
foodSelection('bacon')
print (foodSelection.TotalCalories)
foodSelection('potatoes')
print (foodSelection.TotalCalories)
这是输出：
potatoes : eat as little as possible!
10000
salad : good choice!
10000
bacon : sorry, don't understand that
10000
potatoes : eat as little as possible!
20000
我想保留 运行 用户摄入的总卡路里数，然后将其插入数据库，同时提供用户摄入卡路里量的反馈。当我在函数外定义 TotalCalories 并将其设置为全局变量（以便它可以在另一个函数内使用）时，我得到错误 UnboundLocalError: local variable 'TotalCalories' referenced before assignment
def FoodSelection(choice):
global CurrentPupil
CurrentPupil = ""
global FoodSelectionWindow
FoodSelectionWindow = Toplevel()
FoodSelectionWindow.configure(bg="black")
DateAdded = datetime.date.today()
TimeTaken = 0
NoFoodOption = 0
#The validation timer starts here:
while TimeTaken < 2:
time.sleep(60)
TimeTaken = TimeTaken +1
#and ends here
class food():
def __init__(self, name = "no name", calories = 0, photo = ""):
self.name = name
self.calories = calories
self.photo = photo
BoiledEggs = food("Boiled Egg", 155, PhotoImage(file="BoiledEgg.gif"))
ScrambledEggs = food("Scrambled Egg", 148, PhotoImage(file="ScrambledEgg.gif"))
FriedEggs = food("Fried Egg", 196, PhotoImage(file="FriedEgg.gif"))
PoachedEggs = food ("Poached Egg", 143, PhotoImage(file="PoachedEgg.gif"))
Toast = food("Toast", 313, PhotoImage(file="Toast.gif"))
Bacon = food("Bacon", 514, PhotoImage(file="Bacon.gif"))
Cereal = food("Cereal", 379, PhotoImage(file="Cereal.gif"))
Porridge = food("Porridge", 68, PhotoImage(file="Cereal.gif"))
NoBreakfast = food("No Breakfast", 0, PhotoImage(file="NoBreakfast.gif"))
def NoFood():
FoodChoices("No Food")
def BoiledEggsFunct():
FoodChoices("Boiled Eggs")
def FriedEggsFunct():
FoodChoices("Fried Eggs")
def ScrambledEggsFunct():
FoodChoices("Scrambled Eggs")
def PoachedEggsFunct():
FoodChoices("Poached Eggs")
def ToastFunct():
FoodChoices("Toast")
def BaconFunct():
FoodChoices("Bacon")
def CerealFunct():
FoodChoices("Cereal")
def PorridgeFunct():
FoodChoices("Porridge")
global TotalCalories
TotalCalories = 0
def FoodChoices(selection):
if selection == "No Food":
TotalCalories = NoBreakfast.calories
elif selection == "Boiled Eggs":
TotalCalories = BoiledEggs.calories + TotalCalories
elif selection == "Fried Eggs":
TotalCalories = FriedEggs.calories + TotalCalories
elif selection == "Scrambled Eggs":
TotalCalories = ScrambledEggs.calories + TotalCalories
elif selection == "Poached Eggs":
TotalCalories = PoachedEggs.calories + TotalCalories
elif selection == "Toast":
TotalCalories = Toast.calories + TotalCalories
elif selection == "Bacon":
TotalCalories = Bacon.calories + TotalCalories
elif selection == "Cereal":
TotalCalories = Cereal.calories + TotalCalories
elif selection == "Porridge":
TotalCalories = Porridge.calories + TotalCalories
if choice == 'chris':
CurrentPupil = "Chris"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"1"]))
elif choice == 'josh':
CurrentPupil = "Josh"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"2"]))
elif choice == 'sam':
CurrentPupil = "Sam"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"3"]))
elif choice == 'daniel':
CurrentPupl = "Daniel"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupillID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil, "4"]))
elif choice == 'jim':
CurrentPupil = "Jim"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"5"]))
elif choice == 'sean':
CurrentPupil = "Sean"
with db:
cursor.execute(''' INSERT INTO 'Breakfast_History' (CaloriesTotal, DateAddded, PupilNames, PupilID) VALUES (?,?,?,?)''',
([TotalCalories, DateAdded, CurrentPupil,"6"]))
db.commit()
def FeedbackScreen():
FinishWindow = Toplevel()
if TotalCalories > 0 and TotalCalories < 1000:
HealthyLabel = Label(FinishWindow, text = "Congratulations, you are healthy!", font=("Comic Sans MS", 25), fg = "light green",
bg = "black")
HealthyLabel.grid(columnspan=10)
elif TotalCalories > 1000:
UnhealthyLabel = Label(FinishWindow, text = "Try to eat healthier tomorrow. See personalised advice", font=("Comic Sans MS", 25), fg = "yellow",
bg = "black")
UnhealthyLabel.grid(columnspan=10)
elif NoFoodOption == 1:
NoFoodLabel = Label(FinishWindow, text = "Not eating can be harmful to your health. See personalised advice", font=("Comic Sans MS", 25), fg = "red",
bg = "black")
NoFoodLabel.grid(columnspan=10)
else:
Error = Label(FinishWindow, text = "error", font=("Comic Sans MS", 25), fg = "red",
bg = "black")
NoFoodLabel.grid(columnspan=10)
如您所见，我需要在整个代码中的各种函数中使用 TotalCalories，因此我认为通过将其设为全局变量，我可以做到这一点。
有什么建议吗？
这是MCVE你的问题：
global TotalCalories
TotalCalories = 0
def FoodChoices(selection):
if selection == "No Food":
TotalCalories = 100
elif selection == "Boiled Eggs":
TotalCalories = 100 + TotalCalories
FoodChoices("Boiled Eggs")
运行 此代码产生此输出：
$ python test.py
Traceback (most recent call last):
File "test.py", line 13, in <module>
FoodChoices("Boiled Eggs")
File "test.py", line 11, in FoodChoices
TotalCalories = 100 + TotalCalories
UnboundLocalError: local variable 'TotalCalories' referenced before assignment
并在函数中插入 global TotalCalories 使其消失：
def FoodChoices(selection):
global TotalCalories
if selection == "No Food":
TotalCalories = 100
elif selection == "Boiled Eggs":
TotalCalories = 100 + TotalCalories
Python 要求在要使用它的函数中声明一个全局名称，如果您打算重新绑定全局。如果您只是从中读取或改变它，那么您可以在函数中不声明。
您可能没有考虑过替代方案。在 Python 中，出于某些目的，您可以使对象看起来像函数。然后，您可以积累在对象变量中调用函数时收集到的信息。那么在您的情况下， TotalCalories 可能是对象中的变量。诀窍是为对象中的方法使用名称 __call__；变成 'callable'.
class FoodSelection:
def __init__ (self):
self.TotalCalories = 0
def __call__ (self, choice):
if choice == 'potatoes':
print (choice, ''': eat as little as possible!''')
self.TotalCalories += 10000
elif choice == 'salad':
print (choice, ': good choice!')
self.TotalCalories += 0
else:
print (choice, ''': sorry, don't understand that''')
foodSelection = FoodSelection()
foodSelection('potatoes')
print (foodSelection.TotalCalories)
foodSelection('salad')
print (foodSelection.TotalCalories)
foodSelection('bacon')
print (foodSelection.TotalCalories)
foodSelection('potatoes')
print (foodSelection.TotalCalories)
这是输出：
potatoes : eat as little as possible!
10000
salad : good choice!
10000
bacon : sorry, don't understand that
10000
potatoes : eat as little as possible!
20000