a python beginner here. My previous programming experience is with basic in the eighties, and logic programming in a proprietary system, neither of which is much help for learning python. So, to my question:
I'm writing a math quiz program (just for learning), and I've made a "main menu" by defining a function block; within it, if input is a then another func addition() is called, if input is s then func subtraction() is called and this works as intended. Within those function blocks, I'm setting a global variable quiztype to name of that function. Then I call yet another function again() from within those, to query if user wants another question of the same sort, if yes, I try to return to the relevant function with quiztype () and this fails with TypeError: 'str' object is not callable.
I did find some seemingly-related topics but either couldn't implement the answers or didn't even understand what they were talking about as I'm a beginner.
What options do I have for returning to the previously executed function?
Here's the code: (notice that variable names are not what above - different language)
from random import randint
def Alku ():
kysy = True
while kysy:
lasku = input('Yhteen, Vähennys, Lopeta? ')
if lasku == 'y':
Yhteenlasku ()
kysy = False
elif lasku == 'l':
break
kysy = False
def Uudestaan ():
kysy = True
while kysy:
samauudestaan = input('uudestaan? (k/e)? ')
if samauudestaan == 'k':
Lasku()
kysy = False
elif samauudestaan == 'e':
Alku ()
kysy = False
def Yhteenlasku ():
global Lasku
Lasku='Yhteenlasku'
n1=(randint(1,10))
n2=(randint(1,10))
a1=n1+n2
print(n1, end="")
print(" + ", end="")
print (n2, end="")
print(" = ", end="")
a2=int(input())
print()
if a1==a2:
print('oikein!')
elif a1!=a2:
print('väärin!')
Uudestaan()
Alku ()
And what is returned in terminal:
Traceback (most recent call last):
File "laskut2.py", line 43, in <module>
Alku ()
File "laskut2.py", line 8, in Alku
Yhteenlasku ()
File "laskut2.py", line 41, in Yhteenlasku
Uudestaan()
File "laskut2.py", line 19, in Uudestaan
Lasku()
TypeError: 'str' object is not callable
Your code is fine as it stands, although your global declaration is in an odd place. Still, remove the inverted comma's around your definition of Lasku which is defining it as a string and it will work.
global Lasku
Lasku=Yhteenlasku
P.S. Welcome back to programming!
In response to your question, globals would normally be declared at the beginning of your code or when the data to define becomes available but in this case you are defining it as a function, so you can't define it until the function has been defined. I guess as long as it works, where it is is fine. Personally, in this case, I'd define it here:
global Lasku
Lasku=Yhteenlasku
Alku ()
We really need to see your code to see what you want to achieve but from the sound of it you want to do something like this. From the question it look like you will be recalling function within functions and returning functions, creating recursions which is not that pythonic and also will eventually throw errors and the other is not really needed in this situation. jedruniu has put really quite a good explanation on function variable assignment too.
Less robust version:
def addition():
pass # Put code here
def subtraction():
pass # Put code here
def menu():
while True:
cmd = input("Addition or subtraction? (a/s): ")
if cmd == "a":
addition()
elif cmd == "s":
subtraction()
menu()
Other version (w/ score):
def addition():
# Put code here
result = True
return result # Will be added to score, so any integer or True/False
def subtraction():
# Put code here
result = True
return result # Will be added to score, so any integer or True/False
def menu():
score = 0
while True:
cmd = input("Addition or subtraction? (a/s/exit): ").strip().lower()
if cmd == "exit":
break
elif cmd == "a":
score += addition()
elif cmd == "s":
score += subtraction()
else:
print("Unknown option...")
# Do something with score or return score
if __main__ == "__main__":
menu()
You can assign function to a variable (because function is in Python first-class citizen), so effectively, for example:
def fun1():
print("fun1")
def fun2():
print("fun2")
def fun3():
print("fun3")
f1 = fun1
f2 = fun2
f3 = fun3
functions = {
"invoke_f1" : f1,
"invoke_f2" : f2,
"invoke_f3" : f3
}
functions["invoke_f1"]()
function_to_invoke = functions["invoke_f2"]
function_to_invoke()
yields:
fun1
fun2
More reading: https://en.wikipedia.org/wiki/First-class_function
In your specific example, modify your Uudestaan function.
def Uudestaan ():
Lasku = Yhteenlasku #Add this line
kysy = True
while kysy:
samauudestaan = input('uudestaan? (k/e)? ')
if samauudestaan == 'k':
Lasku()
kysy = False
elif samauudestaan == 'e':
Alku ()
kysy = False
because you were trying to invoke string, and this is not possible. Try to invoke type(Lasku) in your case and you'll see that it is of type str. Invoke it in function with my modification and you'll see type of function.
However I am not sure what is going on in this code, is this finnish? swedish?
Related
I'm trying to figure out how to direct a function to a function. What I'm trying to do is answer a prompt question y/n that would run a certain function. When I input y, it will run through both functions instead of only function 1.
Thanks!
def company_type(question, public_company, private_company):
print("Is the target company public on NYSE or NASDAQ?")
prompt = f'{question} (y/n)'
ans = input(prompt)
if ans == 'y':
return (public_company)
if ans == 'n':
print("Please enter financial infomation manually.")
return (private_company)
company_type("public_company", "private_company", 1)
# function 1
def public_company():
return (print("Success 1"))
public_company()
# function 2
def private_company():
return (print("Success 2"))
private_company()
You can absolutely return a function to be used later - this is the essence of functional programming, and the reason to have functions as first class objects in python ~ Guido Van Rossum.
The important thing is to remember that parens mean a function call, whereas no parens mean the function object.
def public_company():
print("we do what public companies do")
def private_company():
print("we do what private companies do")
def choose_company():
ans = input("Is the target company public?")
if ans == 'y':
return public_company # no parens
else:
return private_company # no parens
if __name__ == '__main__':
# assign the returned function to selected_company
selected_company = choose_company()
# calling selected_company() will call the selected function
selected_company() # use parens, this is a function call!
You don't really want to return a function. You just want one function to call another function. That's done like this:
# function 1
def public_company():
return print("Success 1")
# function 2
def private_company():
return print("Success 2")
def company_type(question, public_company, private_company):
print("Is the target company public on NYSE or NASDAQ?")
prompt = f'{question} (y/n)'
ans = input(prompt)
if ans == 'y':
return public_company()
else:
print("Please enter financial information manually.")
return private_company()
company_type("some question", public_company, private_company)
And please note that return statements in Python do not use an extra set of parentheses. That's a C idiom.
Errors:-
function is not a keyword.
We can call a function by:- <function_name>().
# function 1
def public_company():
print("Success")
# function 2
def private_company():
print("Success")
def company_type():
print("Is the target company public on NYSE or NASDAQ?")
prompt = 'Is your company a public company? (y/n)'
ans = input(prompt)
if ans == 'y':
public_company()
if ans == 'n':
print("Please enter financial information manually.")
private_company()
company_type()
I'm reading from a CSV file and created a function that separates the players from that file into 2 lists: experienced and fresh players.
Then, I tried to create another function that would print the length of each list. However, when I run my script and I call for the 2 functions, Python returns an error saying that the variables of the second function are not defined. Not sure what I'm doing wrong.
import csv
with open('soccer_players.csv', newline='') as csvfile:
players_reader = csv.DictReader(csvfile, delimiter=',')
players = list(players_reader)
def separate(players):
experienced = []
fresh = []
for player in players:
if player['Soccer Experience'] == 'YES':
experienced.append(player)
else:
fresh.append(player)
return experienced, fresh
def countexperience (experienced, fresh):
players_experience = len(experienced)
players_fresh = len(fresh)
print(players_experience)
print(players_fresh)
while True:
start = input("Want to start? (Y/n) ").lower()
if start == "y":
separate(players)
countexperience(experienced, fresh)
break
elif start == "n":
print("goodbye")
break
else:
print("letter not accepted! Please write 'Y' to start or 'N' to exit!\n")
Result:
countexperience(experienced, fresh)
NameError: name 'experienced' is not defined
The local variables in separate() are not added to the current scope, so you need to assign the return of separate() to variables in the current scope, e.g.:
experienced, fresh = separate(players)
Note: you can use any names you want, e.g.
e, f = separate(players)
countexperience(e, f)
You can also expand the tuple return from separate() directly in the function call to countexperience() using *, e.g.:
countexperience(*separate(players))
def letterChoice():
playerLetter = input('Please choose X or O.').upper()
if playerLetter in ['X','O']:
print('The game will now begin.')
while playerLetter not in ['X','O']:
playerLetter = input('Choose X or O.').upper()
if playerLetter == 'X':
computerLetter = 'O'
else:
computerLetter = 'X'
turnChooser()
def turnChooser():
choice = input("Would you like to go first, second or decide by coin toss?(enter 1, 2 or c) ")
while choice not in ["1","2","c"]:
choice = input("Please enter 1, 2 or c. ")
if choice == 1:
print("G")
cur_turn = letterChoice.playerLetter()
elif choice == 2:
print("H")
else:
print("P")
moveTaker()
I can't figure out how I'm supposed to inherit playerLetter into turnChooser(), I've tried putting playerLetter into the brackets of each function but they don't pass and create an argument error and the print("G") and so on are simply there to see if the code works but whenever I enter 1 or 2 "P" is outputted.
You need to define function Attributes for playerLatter
For EX:
def foo():
foo.playerletter=input('Please choose X or O.').upper()
>>> foo()
Please choose X or O.x
>>> foo.playerLetter
'X'
Accessing from another function
def bar():
variable=foo.playerLetter
print(variable)
>>> bar()
X
>>>
You can always check what Attributes are available for a given function
>>> [i for i in dir(foo) if not i.startswith('_')]
['playerLetter']
>>>
Edit turnchooser() to turnchooser(var), then when calling the function pass the letter to the function like this:
def LetterChoice():
Code...
turnchooser(playerletter)
And,
def turnchooser(var):
Code...
The letter will be placed in a variable called var, which means your code will use the letter as var not playerletter.
Of Course you can change the names to whatever you like.
You could add as many variables to the function however they all should have something assigned to them, aka you can't call the previous function like so:
turnchooser()
Unless you assign it a default value:
def turnchooser(var = 'x')
This way whenever the function is called the value of "var" is x unless stated otherwise.
Note that if you want to pass it from one function to another, u either have to assign the letter to a variable then call the function outside the "LetterChoice" or call it in the definition of "LetterChoice"
Within the function that has the variable in it type:
global variableName
Obviously change variableName to whatever the variable is actually called. Hope this helps!
Tommy
You should try using classes: Python documentation
This should be the code:
class Game:
def __init__(self):
self.cur_turn = ''
self.choise = ''
self.playerLetter = ''
self.computerLetter = ''
def letterChoice(self):
while True:
self.playerLetter = input('Please choose X or O.').upper()
if self.playerLetter in ['X','O']:
print('The game will now begin.')
if playerLetter == 'X':
self.computerLetter = 'O'
else:
self.computerLetter = 'X'
break
else:
print ('Please enter only X or O')
def turnChooser(self):
while True:
self.choice = input("Would you like to go first, second or decide by coin toss? (enter 1, 2 or c) ")
if self.choice in ["1","2","c"]:
if self.choice == 1:
print("G")
self.cur_turn = self.playerLetter()
elif self.choice == 2:
print("H")
else:
print("P")
break
else:
print ('Please enter 1, 2 or c')
game = Game()
game.letterChoice()
game.turnChooser()
# If you want to read any of the variables in Game just write 'self.VARIABLE_NAME'
I'm still pretty new to Python, but it seems I've run into a problem. I get an undefined error when trying to call another function that defines that variable.
def unpackCon():
unpackConfirm = input("Unpack contents?[Y/N] ")
def unpackConScript():
if unpackConfirm == "y":
print ("Unpack confirmed.")
elif unpackConfirm == "n":
print ("Unpack unconfirmed.")
else:
print ("Value %s is not valid.") % (unpackConfirm)
unpackCon()
unpackCon()
unpackConScript()
Knowing Python, it's probably got something to do with indentation and the sorts. At first I believed it was because I called the function without defining it first, but I switched around the orders a bunch of times with no result.
Appreciate an answer!
unpackConfirm is defined inside of unpackCon(), and is out of scope in the other function. You need to return the variable in order to access it.
try:
def unpackCon():
unpackConfirm = input("Unpack contents?[Y/N] ").lower()
return unpackConfirm
def unpackConScript():
unpackConfirm = unpackCon()
if unpackConfirm == "y":
print ("Unpack confirmed.")
elif unpackConfirm == "n":
print ("Unpack unconfirmed.")
else:
print ("Value %s is not valid.") % (unpackConfirm)
unpackCon()
unpackConScript()
I am trying to make a program that can add/delete/show students in a class, and the 5 classes are 5 lists in a list.
Help is greatly appreciated.
When I run this code:
global classes
def intro():
print("Welcome to Powerschool v2.0!")
print("Actions:")
print("1. Add Student")
print("2. Delete Student")
print("3. Show Students in a Class")
print("4. Show All Students")
x = int(input())
while x<1 or x>4:
print ("Please choose an action, 1-4.")
x = int(input())
if x == 1:
action1()
elif x == 2:
action2()
elif x == 3:
action3()
elif x == 4:
action4()
classes = [[],[],[],[],[]]
return classes
def action1():
print("Which Class? 1-5")
a = int(input())
print("Please enter the student's name.")
z = input()
classes[a-1].append(z)
again()
def action2():
print ("Which Class? 1-5")
print ("Which student?")
again()
def action3():
print ("Which Class? 1-5")
y = int(input())
if y == 1:
print (classes[0])
elif y == 2:
print (classes[1])
elif y == 3:
print (classes[2])
elif y == 4:
print (classes[3])
elif y == 5:
print (classes[4])
again()
def action4():
print (classes)
again()
def again():
print("Would you like to do something else? y/n")
h = input()
if h == "y":
intro()
else:
quit
def main():
intro()
main()
My error is:
Traceback (most recent call last):
File "C:\Documents and Settings\user1\My Documents\Downloads\az_studenttracker.py", line 67, in <module>
main()
File "C:\Documents and Settings\user1\My Documents\Downloads\az_studenttracker.py", line 65, in main
intro()
File "C:\Documents and Settings\user1\My Documents\Downloads\az_studenttracker.py", line 19, in intro
action1()
File "C:\Documents and Settings\user1\My Documents\Downloads\az_studenttracker.py", line 33, in action1
classes[a-1].append(z)
NameError: name 'classes' is not defined
I did return classes at the end of intro() but I see that doesn't work.
I followed some suggestions, and nothing really happened :/
You're defining classes in your intro method, and, even though it's returning it, your action1 method doesn't see any variable named classes anywhere.
Relevant answer on Python scope and relevant documentation.
return doesn't do what you think it does. return statements are a way of passing execution control back up a context (For example, from intro() to main()), with the ability to send back some information for the higher context to use. Although you're passing classes back to main(), you never do anything with it at that context so it goes away.
One way to solve the problem would be to declare classes as a global variable. This is the easiest thing to do, but isn't generally good design. You could do this either by using the global keyword before declaring the local variable classes in intro() (See this question for guidance on global), or by declaring classes outside any of your functions.
Another solution would be to pass classes as a parameter to your action functions.
In either case, you would need to declare classes before any calls to your action functions.
This is because classes is out of scope for the second two methods. Therefore, you have two options:
Option 1
Pass classes to the methods action1(), action2(), etc like so:
def action1(classes)
...and the when you call it:
action1(classes) //with the classes var you just made
Option 2 (recommended)
Simply put the classes var outside your methods or declare it global like so:
global classes = [[],[],[],[],[]]
...right before:
def intro()
In general, you should read up on how return works; it is not necessary in the code you wrote
classes only exists in intro():, you would have to declare it as a global variable to access it in other functions or declare it outside the function.
classes = [[],[],[],[],[]] # can be accessed by action3() ,action4()
def intro():