Код Python для перехода страниц не работает. Понятия не имею, почему ⇐ Python

[Anonymous]

Контекст: необходимо создать код для проверки размера пакета и прочего.
Проблема: я создал меню для переключения между страницами, и оно не меняется, постоянно повторяя страницу проверки пакета. >

Код: Выделить всё

# Retro Style Turn on Interface For a bit of IBM Style :)

print(":/\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\：")
print(":| Program: [MAIL] Monitoring and Inspection of Logistic    V.1|：")
print(":\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\/：")

# Login Screen For Addressing User
print("\n\t\t\t「Login」")

# Set A whole lot of variable
username = ''
letter = ''
next_page = ''
page = 0
main_page = 0
check_page = 0
parameter_page = 0
history_page = 0
exit_page = 0

# Use While Loop just in case, User entered nothing
while username == '':
username = input("\nUsername: ")
if username == '':  # Check For Empty
print("Username cannot be empty. Please enter a valid username.")

print("Password: ********") # Password for show only

print("\nWelcome", username)

# Now for the fun of turning on my program
power = input("\nRun Program: MAIL (Y)/(N)")

# Checking For User Input again....
while power != 'Y' and power != 'N':
print("Please enter only 'Y' or 'N'")
power = input("\nRun Program (Y/N): ")
main_page = 1

if power == 'N':
print("Shutting Down Program...")
print("Have a Wonderful Day", username)
main_page = 0

elif power == 'Y':
print("Program Status: Running...")
print("...")
print("\n __________________________________________________________ ")
print("|                                                          |")
print("| Welcome to [MAIL], Monitoring and Inspection of Logistic |")
print("|__________________________________________________________|")
main_page = 1

# The actual menu for my program. FINALLY!
while main_page == 1:
print("\nGood day", username)
print("\npress\tA... Parcel Checking")
print("\tB... Parcel Parameters")
print("\tC... Parcel History")
print("\tD... Shut Down")
letter = input("\nPress any LETTER key.")

# Checking again for User input...
while letter != 'A' and letter != 'B' and letter != 'C':
print("\nPlease enter only the LETTER shown")
print("\npress\tA... Parcel Checking")
print("\tB... Parcel Parameters")
print("\tC... Parcel History")
print("\tD... Shut Down")
letter = input("\nPress any LETTER key.")

# Turn Page on and Off Type
if letter == 'A':
check_page = 1
main_page = 0

elif letter == 'B':
parameter_page = 1
main_page = 0

elif letter == 'C':
history_page = 1
main_page = 0

elif letter == 'D':
exit_page = 1
main_page = 0

# This is the input/checking page
while check_page == 1:
print("\n\t\t\tParcel Checking")
print("Enter the following parameters for checking in (cm)")
length = input("Length> ")
while not length.isdigit() or float(length)  80:
if not length.isdigit():
length = input("False Parameters Detected. Enter LENGTH>")
elif float(length) > 80:
length = input("Parameters Violated. More than 80cm Detected. Enter LENGTH> ")

width = input("Width> ")
while not width.isdigit() or float(width)  80:
if not width.isdigit():
width = input("False Parameters Detected. Enter WIDTH once more.")
elif float(width) > 80:
width = input("Parameters Violated. More than 80cm Detected. Enter WIDTH> ")

height = input("Height> ")
while not height.isdigit() or float(height)  80:
if not height.isdigit():
height = input("False Parameters Detected.  Enter HEIGHT once more.")
elif float(height) > 80:
height = input("Parameters Violated. More than 80cm Detected. Enter HEIGHT> ")

weight = input("Weight> ")
while not weight.isdigit() or float(weight)  10:
height = input("Parameters Violated. More than 10Kg. Detected. Enter HEIGHT> ")

next_package = input("Input Next Package (Y)/(N)")

while next_package != 'Y' and next_package != 'N':
print("Please enter only 'Y' or 'N'")
next_package = input("Input Next Package (Y)/(N)")

if next_package == 'Y':
check_page == 1
main_page == 0

elif next_package == 'N':
check_page == 0
main_page == 1

Я возился с последней частью, думая, что у меня есть код под другими кодами, но либо он повторялся, либо перестал что-либо печатать, как будто в коде произошел разрыв.>

Подробнее здесь: https://stackoverflow.com/questions/792 ... o-clue-why