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why does this python while loop not work in the program?

I'm trying to run the program in the following article:
https://blockgeeks.com/guides/python-blockchain-2/
I've copied all of the code into my Spyder IDE. When i run it there's a while loop which starts up asking the user to choose a number from the list of options it prints.
After selecting a number the program should perform the requested action. When i select it though it just loops back to the start of the while loop.
It appears to be ignoring the rest of the code in the while loop (the if statement part).
Confusingly if i take the parts of the code from the program which are used in the while loop and run them separately they work i.e if i run the below code and select the number 1 for my choice it will run the code in the if statement.
Why would the if statement run here but not in the main program?
#function 1:
def get_user_choice():
user_input = input("enter a number: ")
return user_input
#function 2:
def get_transaction_value():
tx_recipient = input('Enter the recipient of the transaction: ')
tx_amount = float(input('Enter your transaction amount '))
return tx_recipient, tx_amount
while True:
print("Choose an option")
print('Choose 1 for adding a new transaction')
print('Choose 2 for mining a new block')
print('Choose 3 for printing the blockchain')
print('Choose anything else if you want to quit')
user_choice = get_user_choice()
if user_choice == '1':
tx_data = get_transaction_value()
print(tx_data)
Update:
Sorry i realise i may not have been very clear what the problem is.
The above code is part of the code from the entire program and runs as expected in isolation from the main program.
The below code is the entire program from the article in the link. It includes all of the code in the program. If i run this main program the while loop doesn't use the if statement. It appears to just be breaking straight out of the loop after i select 1, 2 or 3 (any other number should break out of the loop anyway).
Here's a link for a screen shot showing what the console looks like after i have selected the number 1 for the option.
https://ibb.co/RNy2r0m
# Section 1
import hashlib
import json
reward = 10.0
genesis_block = {
'previous_hash': '',
'index': 0,
'transaction': [],
'nonce': 23
}
blockchain = [genesis_block]
open_transactions = []
owner = 'Blockgeeks'
def hash_block(block):
return hashlib.sha256(json.dumps(block).encode()).hexdigest()
# Section 2
def valid_proof(transactions, last_hash, nonce):
guess = (str(transactions) + str(last_hash) + str(nonce)).encode()
guess_hash = hashlib.sha256(guess).hexdigest()
print(guess_hash)
return guess_hash[0:2] == '00'
def pow():
last_block = blockchain[-1]
last_hash = hash_block(last_block)
nonce = 0
while not valid_proof(open_transactions, last_hash, nonce):
nonce += 1
return nonce
# Section 3
def get_last_value():
""" extracting the last element of the blockchain list """
return(blockchain[-1])
def add_value(recipient, sender=owner, amount=1.0):
transaction = {'sender': sender,
'recipient': recipient,
'amount': amount}
open_transactions.append(transaction)
# Section 4
def mine_block():
last_block = blockchain[-1]
hashed_block = hash_block(last_block)
nonce = pow()
reward_transaction = {
'sender': 'MINING',
'recipient': owner,
'amount': reward
}
open_transactions.append(reward_transaction)
block = {
'previous_hash': hashed_block,
'index': len(blockchain),
'transaction': open_transactions,
'nonce': nonce
}
blockchain.append(block)
# Section 5
def get_transaction_value():
tx_recipient = input('Enter the recipient of the transaction: ')
tx_amount = float(input('Enter your transaction amount '))
return tx_recipient, tx_amount
def get_user_choice():
user_input = input("Please give your choice here: ")
return user_input
# Section 6
def print_block():
for block in blockchain:
print("Here is your block")
print(block)
# Section 7
while True:
print("Choose an option")
print('Choose 1 for adding a new transaction')
print('Choose 2 for mining a new block')
print('Choose 3 for printing the blockchain')
print('Choose anything else if you want to quit')
user_choice = get_user_choice()
if user_choice == 1:
tx_data = get_transaction_value()
recipient, amount = tx_data
add_value(recipient, amount=amount)
print(open_transactions)
elif user_choice == 2:
mine_block()
elif user_choice == 3:
print_block()
else:
break
[1]: https://i.stack.imgur.com/FIrn7.png

When comparing values, Python takes a stronger route regarding data types than some other languages. That means no string in Python will equal a number.
Or in other terms "1" == 1 will be False.
That means you have to consider that in Python 3 you will receive a string from input() (not necessarily so in Python 2).
You can either compare this directly to another string:
user_choice = input()
if user_choice == "1":
print("You chose item 1")
Or you can convert it into a number first and compare it to a number:
user_choice = int(input())
if user_choice == 1:
print("You chose item 1")
Note that in the former case it might not be robust if the user enters extra spaces and in the latter case it will fail very loudly with an exception if the user doesn't enter an integer (or even nothing at all).
Both ways can be handled with extra code if necessary. In the former case, you can strip whitespace with user_input = input().strip() and in the latter case you can catch the exception with a try ... except ... block.

You have only handled the case for user_choice == '1'. If you enter anything other than 1, the program will return control to the beginning of the while loop.
I'll suggest you use a debugger to see what user_choice is before the if condition. If not, just use prints.
print("user_choice: {}, type: {}".format(user_choice, type(user_choice))

How to write to a text file using iteration?

My code does not write to a file, what am I doing wrong? I am trying to program to continue to ask for products until the user does not enter a product code. I want all products to be saved in the file.
store_file = open("Database.txt", "w")
NewProduct = ""
while NewProduct != False:
contine = input("Press 1 to enter a new product press 2 to leave: ")
if contine == "1":
print("Enter your product information")
information = []
product = input("What's the product code: ")
information.append(product)
description = input("Give a description of the product: ")
information.append(description)
price = input("Enter price of product: ")
information.append(price)
information = str(information)
clean = information.replace("]","").replace("[","").replace(",","").replace("'","")
store_file.write(clean)
elif contine == "2":
NewProduct = False
else:
print("Your input is invalid")
store_file.close

I got the program working with the following adjustments. See comments for explanations:
store_file = open("Database.txt", "w")
NewProduct = ""
while NewProduct != False:
continue = raw_input("Press 1 to enter a new product press 2 to leave: ")
#Changed to raw_input because input was reading in an integer for 1 rather than a
#string like you have set up. This could be specific to my IDE
if continue == "1":
print("Enter your product information")
information = []
product = raw_input("What's the product code: ")
information.append(product)
description = raw_input("Give a description of the product: ")
information.append(description)
price = raw_input("Enter price of product: ")
information.append(price)
information = str(information)
clean = information.replace("]","").replace("[","").replace(",","").replace("'","")
store_file.write(clean + "\n")
#Added a line break at the end of each file write
elif contine == "2":
NewProduct = False
else:
print("Your input is invalid")
store_file.close() #Added parentheses to call the close function

I'm assuming the problem here is that you're using Python 2, and input isn't doing what you think it does. In Python 2, input evals the input as if it were Python source code, so if someone enters 2, it's going to return the int value 2, not "2". In Python 2, you want to use raw_input, always (eval-ing random user input not being secure/reliable).
Also, while on CPython (the reference interpreter) files tend to naturally close themselves when they go out of scope, you made an effort to close, but forgot to actually call the close method; store_file.close looks up the method without calling it, store_file.close() would actually close it. Of course, explicit close is usually the wrong approach; you should use a with statement to avoid the possibility of forgetting to close (or of an exception skipping the close). You can replace:
store_file = open("Database.txt", "w")
...
store_file.close()
with:
with open("Database.txt", "w") as store_file:
... do all your work that writes to the file indented within the with block ...
... When you dedent from the with block, the file is guaranteed to be closed ...
There are other issues though. What you're doing with:
information = str(information)
information = information.replace("]","").replace("[","").replace(",","").replace("'","")
is terrible. I'm 99% sure what you really wanted was to just join the inputs with spaces. If you switch all your input calls to raw_input (only on Python 2, on Python 3, input is like raw_input on Python 2), then your list is a list of str, and you can just join them together instead of trying to stringify the list itself, then remove all the list-y bits. You can replace both lines above with just:
information = ' '.join(information)

python input check function not being called properly

I'm working on a very simple temperature converter in Python (just for practice), and am struggling with some of the UX components. I'd like to have checks in place to continue prompting for variable input when invalid entries are made. My full code is below:
o_temp = ''
def temp_input(o_temp):
o_temp = raw_input('Enter a temperature (round to nearest integer): ')
return o_temp
def temp_input_check(o_temp):
o_temp = list(o_temp)
for i in o_temp:
if i not in '1234567890':
print 'Invalid entry. Please enter only the numerical temperature measurement in integer format.'
temp_input(o_temp)
else:
break
def converter(o_temp):
unit = raw_input('Convert to (F)ahrenheit or (C)elsius? ')
unit = unit.upper()
if unit == 'F' or unit == 'f':
n_temp = (9.0/5.0) * int(o_temp) + 32
print '%d C = %d F' % (o_temp, n_temp)
quit()
elif unit == 'C' or unit == 'c':
n_temp = (5.0/9.0) * (int(o_temp) - 32)
print '%d F = %d C' % (o_temp, n_temp)
quit()
else: #check for valid entry
print 'Invalid entry. Please enter F for Fahrenheit or C for Celsius'
unit_input()
def temp_converter():
#title, call sub-functions
print ''
print 'Temperature Converter'
print ''
temp_input(o_temp)
temp_input_check(o_temp)
converter(o_temp)
temp_converter()
However, when I enter an invalid entry (say, a letter or a combination of letters and numbers) into the o_temp prompt, the code does not seem to recognize that this is invalid and continues with the unit prompt. Am I not correctly returning the variable? What's the issue here? I tried removing the initial o_temp declaration but then I got "NameError: global name 'o_temp' is not defined"
EDIT
I came up with this solution, any further suggestions to refine the code at all?
def converter():
print 'Temperature Converter'
while 1:
temp = raw_input('Starting temperature? ')
try:
temp = float(temp)
except ValueError:
print 'Invalid entry. Please enter only the numerical temperature measurement.'
else:
break
while 1:
unit = raw_input('Convert to Fahrenheit or Celsius? ')
if unit.upper().startswith('F') == True:
print "%f C = %f F" % (temp, temp*9./5+32)
return False
elif unit.upper().startswith('C') == True:
print "%f F = %f C" % (temp, (temp-32)*5./9)
return False
else:
print 'Invalid entry. Please enter F for Fahrenheit or C for Celsius'
converter()

You define some functions, then call temp_coverter(). This function calls temp_input(otemp), sending it an empty string for no reason that I can see, other than the possibility that you're unaware that you can define a function with no parameters. This function then returns a value, which you don't save.
After that, temp_input_check(otemp) is called, which attempts to validate the same empty string. This function's returned value isn't saved, which isn't a big loss, because None isn't a particularly useful value to save.
Then converter(otemp) sends the same old empty string to the actual converter. Mayhem results.
I recommend spending some quality time with the tutorial.
When you're done, the code should look more like this:
def converter():
print 'Temperature Converter'
unit = raw_input('Convert to Fahrenheit or Celsius? ')
while 1:
temp = raw_input('Starting temperature? ')
try:
temp = float(temp)
except ValueError:
print 'Not a valid temperature.'
else:
break
if unit.lower().startswith('f'):
print "%f C = %f F" % (temp, temp*9./5+32)
else:
print "%f F = %f C" % (temp, (temp-32)*5./9)
converter()

Your for loop isn't implemented correctly.
def temp_input_check(o_temp):
o_temp = list(o_temp)
for i in o_temp:
if i not in '1234567890':
print 'Invalid entry. Please enter only the numerical temperature measurement in integer format.'
temp_input(o_temp)
else:
break
You check every character for an invalid entry. If you typed in multiple invalid characters, it'll keep hitting the trigger after you have already determined that the string is invalid!
Also, if your first character is valid, you're telling it to break from the for loop (in your code 1fdsdfdsf would be a valid temperature, because it would skip every character after hitting that else statement and breakout from the loop).
Also, your temp_input doesn't need to accept an argument in the function (you're just gonna return the user's input). You actually want to assign it after you call the function instead of having it as an argument
Also, you're calling temp_input again to get the user input, but not capturing that anywhere with a return - so it's ultimately not doing anything. You should have your function return a True or False, and then catch that on the outside of the checker if you want to have the user try and enter a better temperature:
def temp_input_check(o_temp):
o_temp = list(o_temp)
for i in o_temp:
if i not in '1234567890':
print 'Invalid entry. Please enter only the numerical temperature measurement in integer format.'
return False
else:
pass # nothing is wrong with this character, keep checking
return True # if we hit this line, there were no problem characters
Then, when you call the stuff:
while(1):
o_temp = temp_input()
if temp_input_check(o_temp):
break # this means our o_temp is allllright.
# otherwise, go back to the start of the loop and ask for another temp
converter(o_temp)

because you mentioned 'o_temp' as the function parameter in the end but mentioned it as a empty string at Start. Don't give same names for global & function variables (just to avoid confusion). the function took the o_temp you mentioned above as parameter and neglects the one inside them.
Also the raw_input won't consider the input as string. Try input instead to avoid the sensibility of not using str to correct the loop.
This will do:
def converter():
o_temp = float(raw_input('Enter a temperature (round to nearest integer): '))
for i in str(o_temp):
if i not in ['1','2','3','4','5','6','7','8','9','0','.']:
print 'Invalid entry. Please enter only the numerical temperature measurement in integer format.'
unit = raw_input('Convert to (F)ahrenheit or (C)elsius? ')
if unit in ['f','F']:
n_temp = (9.0/5.0) * float(o_temp) + 32
print '%f C = %f F' % (o_temp, n_temp)
elif unit in ['c','C']:
n_temp = (5.0/9.0) * (float(o_temp) - 32)
print '%f F = %f C' % (o_temp, n_temp)
else: #check for valid entry
print 'Invalid entry. Please enter F for Fahrenheit or C for Celsius'
unit_input()
def temp_converter():
#title, call sub-functions
print ''
print 'Temperature Converter'
print ''
converter()
print temp_converter()

Problems transferring information from one part of a function to another

While working on my program I have run into a problem where the information stored in Menu option 1 is not being transferred to Menu option 2. As you can see it is correctly stored when in menu one. When it returns to go to menu option 2 its like it never went to option 1.
update #1:
some suggestions I've had is to understand scope? from what I can tell the program is not passing the data along to its parent program even though I've typed out return in each of the definitions.
#Must be able to store at least 4 grades
#Each class can have up to 6 tests and 8 hw's
#Weighted 40%*testavg 40% hw average attendance is 20%
#User must be able to input a minimum grade warning
#after each test the your program must calculate the students average and issue warning if necessary
##Define the Modules##
import math
def menu (a): #2nd thing to happen
menuend = 'a'
while menuend not in 'e':
menuend = raw_input("Type anything other then 'e' to continue:\n")
print "What would you like to do ?"
menudo = 0
print "1 - Enter Courses\n2 - Select Course to Edit\n3 - Save File\n4 - Load File\n5 - Exit\n"
menudo = input("Enter Selection:")
if (menudo == 1):
menuchck = 0
menuchck = raw_input("\nYou have entered #1 (y/n)?:\n")
if menuchck in ["Yes","yes","y","Y"]:
x = m1()
else:
print "I'm sorry,",nam,",for the confusion, lets try again\n"
menu()
elif (menudo == 2):
menuchck1 = 0
menuchck1 = raw_input("\nYou have entered #2 (y/n)?:\n")
if menuchck1 in ["Yes","yes","y","Y"]:
x = m2()
else:
print "I'm sorry,",nam,",for the confusion, lets try again\n"
menu()
elif (menudo == 3):
print "Entered 3"
elif (menudo == 4):
print "Entered 4"
else:
print "Anything Else Entered"
def course(): #3rd thing to happen
b = {}
while True:
while True:
print "\n",name,", please enter your courses below ('e' to end):"
coursename = raw_input("Course Name:")
if (coursename == 'e'):
break
will = None
while will not in ('y','n'):
will = raw_input('Ok for this name : %s ? (y/n)' % coursename)
if will=='y':
b[coursename] = {}
print "\n",name,", current course load:\n",b
coursechck = None
while coursechck not in ('y','n'):
coursechck = raw_input("Are your courses correct (y/n)")
if coursechck =='y':
return b
else:
b = {}
print
##Menu Options##
def m1():
a = course()
return a
def m2():
print "Excellent",name,"lets see what courses your enrolled in\n"
print x
return x
###User Input Section###
name = raw_input("Enter Students Name:\n")
a = {}
menu(a)
raw_input("This is the end, my only friend the end")

In your if-elif blocks in the do==1 case, you write m1(), but for the last case, you write x=m1(). You should have the latter everywhere (by typing m1() you only run the function, but do not store the returned x anywhere).
By the way, you can avoid this if-elif confusion using if chck in ["Yes","yes","Y","y"]:

python: global name 'user_input' is not defined

I keep getting the error message "global name 'user_input' not defined. new to python and to SO, hope you can help. Here's my code. Sorry if it's a mess. just starting out and teaching myself...
def menu():
'''list of options of unit types to have converted for the user
ex:
>>> _1)Length
_2)Tempurature
_3)Volume
'''
print('_1)Length\n' '_2)Temperature\n' '_3)Volume\n' '_4)Mass\n' '_5)Area\n'
'_6)Time\n' '_7)Speed\n' '_8)Digital Storage\n')
ask_user()
sub_menu(user_input)
def ask_user():
''' asks the user what units they would like converted
ex:
>>> what units do you need to convert? meter, feet
>>> 3.281
'''
user_input = input("Make a selection: ")
print ("you entered", user_input)
#conversion(user_input)
return user_input
def convert_meters_to_feet(num):
'''converts a user determined ammount of meters into feet
ex:
>>> convert_meters_to_feet(50)
>>> 164.042
'''
num_feet = num * 3.28084
print(num_feet)
def convert_fahrenheit_to_celsius(num):
'''converts a user determined temperature in fahrenheit to celsius
ex:
>>> convert_fahrenheit_to_celsius(60)
>>> 15.6
>>> convert_fahrenheit_to_celsius(32)
>>> 0
'''
degree_celsius = (num - 32) * (5/9)
print(round(degree_celsius, 2))
def sub_menu(num):
'''routes the user from the main menu to a sub menu based on
their first selection'''
if user_input == '1':
print('_1)Kilometers\n' '_2)Meters\n' '_3)Centimeters\n' '_4)Millimeters\n'
'_5)Mile\n' '_6)Yard\n' '_7)Foot\n' '_8)Inch\n' '_9)Nautical Mile\n')
ask = input('Make a selection (starting unit)')
return
if user_input == '2':
print('_1)Fahrenheit\n' '_2)Celsius\n' '_3)Kelvin\n')
ask = input('Make a selection (starting unit)')
return

When you do:
user_input = input("Make a selection: ")
Inside the ask_user() function, you can only access user_input inside that function. It is a local variable, contained only in that scope.
If you want to access it elsewhere, you can globalise it:
global user_input
user_input = input("Make a selection: ")
I think what you were trying was to return the output and then use it. You kind of got it, but instead of ask_user(), you have to put the returned data into a variable. So:
user_input = ask_user()
THere's no need to globalise the variable (as I showed above) if you use this method.

In your menu function, change the line that says ask_user() to user_input = ask_user().