I have been studying beginning game development with pygame and python, and I ran into a snag with defining functions that have arguments. The first one works, and I'm trying to make a more simple version with only one argument. It keeps saying c is not defined when it clearly is. I don't understand why. Any suggestions or ideas on this? I'm also having
def fugu_tip(price, num_plates, tip):
total = price * num_plates
tip = total * (tip / 100.)
return tip
def Character(c):
a = input("Enter a number 1 - 100")
b = input("Enter A Number 1 - 100")
c = 0
c = a + b
return c
Character(c)
I appreciate all the help guys!
This is the revised code for my project:
'$'
import pygame
import random
global Cash
global PName
global PHealth
global PHunger
global PJob
global PEmployeed
def Character1():
Cash = 0
PName = raw_input("Please Enter Name: ")
PHealth = 100
PHunger = 100
PJob = ""
PEmployeed = False
print PName, Cash, PHealth, PHunger, PJob, PEmployeed
Character1()
'$'
I'm going to rework some of the code you have rather than rewriting entirely. The thing that you are missing is scope. Inside, your function, c is defined. However, outside of your function you are trying to pass in a variable called c that is not defined.
Here's your code, fixed up.
#it's true that by convention, functions generally start with lowercase
# and Classes being with uppercase characters
def character(c = 0):
a = input("Enter a number 1 - 100")
b = input("Enter A Number 1 - 100")
return c * (a + b)
myValue = 3 #note that the variable that you pass in
# to your function does not have to have the same name as the parameter
character(myValue)
Note, I modified the behavior of the function so that i makes use of the parameter c. Now, c, the input parameter, is used to multiply the sum of the two user inputs. When I call the function the value of c becomes 3 and so what ever the user enters is added then multiplied by 3.
Also, there is a difference between def character(c): and def character(c=0):. In the first case, a value must be passed into the function when calling it. In the second case, you can skip passing in a value to the function as we have the defined the function with a default argument value. So the second function could be called directly with:
character(3)
character()
But the first could only be called correctly with
character(3)
c is defined inside your function — but not where you call Character.
You seem to set c to 0 in your function anyways — why have any parameter at all then?
Finally, you should not give your functions names that start with capital letters, as by convention that is reserved for classes.
edit:
def get_sum():
a = input("Enter a number 1 - 100")
b = input("Enter A Number 1 - 100")
c = a + b
return c
Well, the problem is c is not defined at current scope. In your case, c is only visible from inside the function Character but not from outside. So, the place from where you are calling the function has no idea what c is. As soon as you define c your code works just fine.
def Character(c):
a = input("Enter a number 1 - 100")
b = input("Enter A Number 1 - 100")
c = 0
c = a + b
return c
c = 0
Character(c)
Or maybe something like this (edit)
def Character(c):
a = input("Enter a number 1 - 100")
b = input("Enter A Number 1 - 100")
c = 0
c = a + b
return c
def call_character():
c = 0
Character(c)
call_character()
The problem is where you call Character(c). That c has not been defined. I can't suggest what you should do instead because I don't know what you are trying to do, but that is your problem. What you use instead depends on what argument you want to give to Character().
C is being passed as a argument to the function Character so it should be defined before you call then function.
You don't need to pass any argument to
Character
as it is not required for given behavior. Simply do
Character()
.
And also remove C from your function definition.
def Character():
a = input("Enter a number 1 - 100")
b = input("Enter A Number 1 - 100")
c = 0
c = a + b
return c
Character()
Edited : based on user comment
Related
a = 0
def add(number):
number += 1
return number
for i in range(20):
add(a)
print(a)
I'm wondering why I get 0 for the print(a) call in the last line.
I put 0 for the first loop of the add()function and it should return 1 and so on in the for loop.
What am I missing?
I think you're just missing assigning the return value of add() back to a. Without the assignment, a never changes because function arguments are passed by value, not reference.
a = 0
def add(number):
number += 1
return number
for i in range(20):
a = add(a)
print(a)
it seems you aren't actually changing the value of a, try changing your for loop to look something like this:
for i in range(20):
a = add(a)
To make use of the return keyword, make sure you understand that it sends back a value to the main program, treat it like another variable.
When you pass an int to a function, you're basically passing a copy of it. So your function adds 1 to a copy of a and returns it, but there's nothing there to catch the returned value.
When you pass a list or dict to a function, you're passing a reference to the original object, though. If you change it inside your function it changes thoughout your code:
a = 0
b = [0]
c = {"engelbert": 0}
def add(number, lst, dct):
number += 1
lst[0] += 1
dct["engelbert"] += 1
# No return statement:
# Function returns `None` by default
for i in range(20):
add(a, b, c)
print(a, b, c)
# 0 [20] {'engelbert': 20}
Is it possible for one function to take as an argument the name of one of the optional arguments of a second function then call the second function with the optional argument set to the value of some variable in the first function?
Code (that obviously doesn't work)
def foo(a=1,b=2,c=3):
d = a + b + c
return d
def bar(variable):
z = get_user_input()
e = foo(variable = z)
return e
print(bar(a))
The desired result is for bar to call foo(a=z) and print whatever z+2+3 is. Of course Python doesn't know what (a) is here. My guess is that I can somehow reference the list of arguments of foo() , but I am stumped as to how you might do that.
Maybe try the code snippet below
def foo(a=1,b=2,c=3):
d = a + b + c
return d
def bar(variable: str):
z = int(input())
e = foo(**{variable: z})
return e
# variable name should be defined as string
print(bar("a"))
The ** parses all arbitrary arguments on dict, in this case is a. Be careful tho, as if passing wrong variable name (differ from a, b or c) will result raising error.
This question already has answers here:
How do I get a result (output) from a function? How can I use the result later?
(4 answers)
Closed 6 months ago.
I know there are several questions about this, I read but I could not understand. I'm trying to use the result of the return of one function in another:
def multiplication(a):
c = a*a
return c
def subtraction(c):
d = c - 2
return d
print(subtraction(c))
Output:
NameError: name 'c' is not defined
I know that there is a possibility of using global variables, but I have seen that this is not a good idea since the variables can change their value.
EDIT:
These two functions are just idiotic examples. I have two functions with words and I need to use the return of the first function in the second function. In case of this my idiotic example, I need the result of the first function (c) in the second function.
You are not calling your functions properly.
def multiplication(a):
c = a*a
return c
def subtraction(c):
d = c - 2
return d
# first store some value in a variable
a = 2
# then pass this variable to your multiplication function
# and store the return value
c = multiplication(a)
# then pass the returned value to your second function and print it
print(subtraction(c))
Does this makes things clearer?
def multiplication(a):
c = a*a
return c
def subtraction(c):
d = c - 2
return d
print(multiplication(5)) # 25
print(subtraction(5)) # 3
print(multiplication(subtraction(5))) # 9
print(subtraction(multiplication(5))) # 23
I think you're trying to do what's happing in the last print statement: first call the multiplication function, and then call the subtraction function on the result.
Note that the variable c in your multiplication function is an entirely different variable from the c in your subtraction function. So much so, that it may make things more clear to rename your variables, perhaps something like this:
def multiplication(a):
product = a * a
return product
def subtraction(a):
difference = a - 2
return difference
So why not use return value?
print(subtraction(multiplication(24)))
?
'c' is not declared outside the 'subtraction' function.
You need to give need to declare 'c' before printing.
Let's say you want 'c' to be 5, then:
c = 5
print(subtraction(c))
You have defined two functions which both return a number.
If you call subtraction(c) you will get the error you see, because there is no c.
If you define a c in scope of the print statmenet
c = 42
print(subtraction(c))
it will be ok.
Try thinking of it like this: each function takes a variable does things to it and returns a number.
e.g.
>>> multiplication(101)
10201
That this happened to be called c isnide the function isn't known outside the function (i.e scope).
You can save the number to a variable
>>> x = multiplication(101)
Then x remembers that value.
Or
>>> c = multiplication(101)
This is not the same c as you have inside the functions.
(And after the question edit):
Decide what value you want to call the first function with, for example 101:
>>> c = multiplication(101)
then use that return to call the next function:
>>>> subtraction(c)
Or just chain them togther:
subtraction( multiplication(101) )
To start the chain you will need to use a string, int or defined variable.
Otherwise you get name not defined errors.
Once a variable is used in a function it goes out of scope when the function ends.
My code is as follows...
def addition(a, b):
c = a + b
return c
And I then want to be able to use C later on in the program as a variable. For example...
d = c * 3
However, I get a NameError that 'C' is not defined... But I have returned c, so why can I not use it later on in the code?! So confused. Thanks!
(This is obviously a simpler version of what I want to do but thought I'd keep it simple so I can understand the basics of why I cannot call on this variable outside my function even though I am returning the variable. Thanks)
You have returned the value of c but not the whole variable i.e. the name c exists only within the scope it is instantiated.
So, if you want to use the value returned, you should re-assign it to a new name. You can do it by re-assigning it to c again, but it could be any name you wanted.
def addition(a, b):
c = a + b
return c
new_var = addition(1,2) #new_var gets the value 3
c = addition(2,3) #c gets the value 5
Take a look at this nice explanation about variables and scopes (link)
You usually define a function to use it later in your code. For that case, use another global variable c:
def addition(a, b):
c = a + b
return c
c = addition(1, 2)
d = c * 3 # d == 9
Functions allow this usage of repeated code, or procedure distinction, so that you can later write in your code
m = addition(4, 5)
and it will store the required result of the functionality into m.
If you want to define c in the function and use it later, you can use global variables.
c = 0
def addition(a, b):
global c
c = a + b
return c
It's not considered good to use globals, though. You could also call the function in the variable assignment.
d = addition(a, b) * 3
For this, you need to put real numbers in the place of a and b. I recommend you use the second option.
I am a bit confused over this.
I have a function. Inside that function it asks a number of questions, one is the following based on the number of gardens they have - so if they say they have 2 gardens it will ask this question twice and should add the 100 twice to the calculation:
gardens = int(input("How many gardens do you have: "))
def gard():
calc = 0
gardener = input("Do you need a gardener? Y or N ")
if gardener == "Y" or gardener == "y":
calc = calc + 100
else:
calc = calc + 0
for i in range(gardens):
gard()
How do I keep a running total outside of the function? When I put print(calc) inside the function it just displays 100 each time they say Y but doesn't add it together.
Edited to include updated code:
The eMake section (the IF statement) returns a value - but it only ever returns the first in the calculation at the end?
Also struggling to do the area section since there are numerous ws. It only stores the last value for the variable.
noGard = int(input("Enter number of gards which require cleaning: "))
#Defining variables
Calc = 0
Area = 0
emCalc = 0
#Room information
def GInfo():
global Calc
global Area
gName = input("Enter gard name: ")
noW = int(input("How many w are in the "+gName + "? "))
#Repeats the questions for each W
for i in range(noW):
Height = float(input("What is the w height of in metres? "))
Width = float(input("What is the w width in metres? "))
Area = Height * Width
#Asks if w needs to be removed
w = input("Does w need removing? Y or N ")
if w == "Y" or w == "y":
Calc = Calc + 70
else:
Calc = Calc + 0
print (" ")
#Returns the values
return Calc
return Area
#Calculate Sarea
#Identifying e
def e():
global emCalc
#eMake
eMake = input("What make of e - HH or NN? ")
if eMake == "HH" or "hh":
emCalc = emCalc + 200
elif eType == "NN" or "nn":
emCalc = emCalc + 50
else: print("You have entered an invalid e make")
#Returns the values
return emCalc
#Repeats the g information questions for each g
for i in range(noGard):
GInfo()
# Runs the E function
e()
#Print total without VAT
total = Calc + emCalc
print(total)
print(Area)
Your function should return the calculated value.
def gard():
...
return calc
total = 0
for _ in range(gardens):
total += gard()
print 'Total: ', total
The whole point of functions, really, is that they take parameters and return values. (Some languages, although not Python, refer to functions that don't do this as "procedures".)
That is what you need to do here: your gard function needs to return the value of calc. You probably don't want to actually do the addition inside the function itself, but if you did, you would also need to accept the current value of calc as a parameter, which you would pass in from your for loop.
Functions, in the strictest sense, do not have state. When writing functional programs, one typically aims to keep their functions pure, meaning that the result of the function does not depend on anything but its inputs and does not cause observable side effects.
But Python is not a purely functional language. It is an object-oriented procedural language which models functions as objects, and objects can be stateful. So you can do what you're aiming to, if you don't take the word "function" too literally.
The Right Thing™
Create a class which models your data and the operations on it:
>>> class F(object):
... def __init__(self):
... self.x = 0
... def f(self):
... self.x += 1
... return self.x
...
>>> my_f = F()
>>> my_f.f()
1
>>> my_f.f()
2
Fun and naughty ways
Add state to the function object, taking advantage of the fact that function bodies aren't executed until the function is called:
>>> def f():
... f.x += 1
... return f.x
...
>>> f.x = 0
>>> f()
1
>>> f()
2
If you want to do this transparently (that is, make it so that you don't have to add this state to the function right after defining it) you can close over the state by having a function create a function:
>>> def g():
... def func():
... func.x += 1
... return func.x
... func.x = 0
... return func
...
>>> f = g()
>>> f()
1
>>> f()
2
To take it a step further, create a decorator so you don't have to do any assignments after defining the function at all:
>>> def with_x(func):
... func.x = 0
... return func
...
>>> #with_x
... def f():
... f.x += 1
... return f.x
...
>>> f()
1
>>> f()
2
Or you can just use global to let a function refer to something outside of its local scope, not taking advantage of the fact that functions are objects:
>>> x = 0
>>> def f():
... global x
... x += 1
... return x
...
>>> f()
1
>>> f()
2
>>> x
2
Updates for your edit
Since you went with global I'll first refer you to a good question that explains global. Using global variables in a function other than the one that created them
Now, as for your particular problems:
The eMake section (the IF statement) returns a value - but it only ever returns the first in the calculation at the end?
Sure, there are a couple problems here and one of them is definitely a common one for beginners. or takes higher precedence than == so your condition parses like this:
if (eMake == "HH") or ("hh"):
This gets people all the time. In Python, if a value isn't a boolean and you put it in a conditional statement, it gets evaluated as a boolean using a series of truthiness rules. In this case a non-empty string is considered True so you are basically saying if (eMake == "HH") or True.
To fix this, fix the right-hand side of the condition:
if (eMake == "HH") or (eMake == "hh"):
By the way, you probably meant elif (eMake == "NN") or (eMake == "nn"): instead of elif eType == "NN" or "nn": because you never defined eType (and for the reason above, too.) If you type nn there you'll get an exception.
Also struggling to do the area section since there are numerous ws. It only stores the last value for the variable.
This is because you repeatedly assign to the same variable with Area = Height * Width. Since Area is global, it's the same variable every time you call GInfo(). If it wasn't global it would be a new variable every time you called the function, but then you would need to return it and assign the return value to a variable in order to save the value. Otherwise it would disappear since it was never assigned to anything.
Now, I don't know what you are trying to do with the areas you're calculating. Do you want to keep them separate or sum them together?
If you want to keep them separate, you'll need to use a data structure. In this case, you'd definitely want to use a list. Using the append() method of lists, you can add an item to the list. So it would look something like this:
areas = [] # empty list
def GInfo():
global areas
# the stuff before the loop
for i in range(noW):
Height = float(input("What is the w height of in metres? "))
Width = float(input("What is the w width in metres? "))
areas.append(Height * Width)
# the stuff after the loop
If you want to sum them together, just make sure you add each individual area calculation to the previous result, just like you did with Calc:
Area += Height * Width
One more thing: your GInfo() function is only returning Calc and not Area as well. Functions can only return one value. In the mathematical sense, a function is a many-to-one mapping between two sets. So in Python, a function ends at the return statement. Nothing else gets executed after that.
In order to get both the value of Calc as well as the value of Area from the return value of GInfo(), you will have to return a data structure. Usually this would be a tuple.
return (Calc, Area)
But your code doesn't assign the return value of GInfo() to anything. Instead, it uses the global declaration to change the value of the global variables. So there shouldn't be an issue here.