Python: NameError: name 'u' is not defined

Question

i am completing a simple class asignment with functions. We have to find for which month m the functioncontract_v will be more advantageous than the contract_u. This is the code I wrote:

def contract_u(m):
  u=1000
  for i in range (m):
    u=u+80
  return u

def contract_v(m):
  v=1000
  for i in range (m):
    v=v*1.05
  return v

m=1
if u>v:
  m=m+1
else:
  print(m)

However, the computer says this:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-20-8909d368129a> in <module>()
     12 
     13 m=1
---> 14 if u>v:
     15   m=m+1
     16 else:

NameError: name 'u' is not defined

I do not understand what I have to modify and why the code is not functionning properly. If you do know what has been done wrong, please point that out. Thank you in advance.

You can only refer to a variable when it's inside the scope. Here's some more information about [the scopes of variables in Python](https://docs.python.org/3.3/reference/executionmodel.html) — Pranav Hosangadi, Oct 19 '20 at 16:04
Does this answer your question? [Short description of the scoping rules?](https://stackoverflow.com/questions/291978/short-description-of-the-scoping-rules) — Pranav Hosangadi, Oct 19 '20 at 16:05

score 1 · Accepted Answer · answered Oct 19 '20 at 16:02

1

your variables are defined locally in your functions, so they do not exist outside of them, so you should add these lines before your if statement :

u=contract_u(m)
v=contract_v(m)

answered Oct 19 '20 at 16:02

NHL

277
1
6

score -1 · Answer 2 · answered Oct 19 '20 at 16:04

-1

Here you haven't called functions which declares the variable u and v So try like this:

def contract_u(m):
  u=1000
  for i in range (m):
    u=u+80
  return u

def contract_v(m):
  v=1000
  for i in range (m):
    v=v*1.05
  return v

m=1
u = contract_u(m)
v = contract_v(m)
if u>v:
  m=m+1
else:
  print(m)

answered Oct 19 '20 at 16:04

Wasif

14,755
3
14
34

1

One important thing since you struggle with functions: The names of the variables in the function and outside of the function can be different. So you could do `foo = contract_u(m)` and then do the comparison with `if foo > v:`. – Matthias Oct 19 '20 at 16:20
1

Calling the functions has nothing to do with this. `u` and `v` are defined _inside_ the function scope, and assigning the return value of the functions to `u` and `v` outside is what assigns those values to those names outside the function – Pranav Hosangadi Oct 19 '20 at 16:20

Python: NameError: name 'u' is not defined

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