1

Programming beginner here

I am trying to extract a variable of a for loop within a function to be used in the "Di = " equation, as follows:

                def fun1():
                    global de, ep
                    with open("Di_Tub.csv", "r") as f3:
                        reader3 = csv.reader(f3, delimiter=';')
                        i3 = 0
                        for row3 in reader3:
                            i3 = i3 + 1
                            if i3 >= 1:
                                if row3[0] == DN:
                                    if row3[1] == SCH:
                                        de = float(row3[2])
                                        ep = float(row3[3])
                    f3.close()
                fun1()
                Di = (de - 2*ep)/1000

What I get is this error:

Di = (de - 2*ep)/1000
NameError: name 'de' is not defined

What am I doing wrong?

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3
  • try putting : global de = float(row3[2]) and global ep = float(row3[3]) Commented Jun 22, 2020 at 16:54
  • Some questions about this code: why do you need fun1() at all? Function doesn't return anything and if you need variable value(s) then write simple loop without function. On top of that: why do you need i3? What are DN and SCH? You don't need to close file if using context manager (with) Commented Jun 22, 2020 at 17:02
  • Hello Aivar. As said, I'm a beginner in programming. This is just a section os the whole code. DN and SCH are variables previously defined. Because i have other 2 for loops i decided to name the counter here as i3. About fun1(), I wanted to try a new thing other than just writting the for loop, which wasn't working. Commented Jun 22, 2020 at 17:27

3 Answers 3

Reset to default
1

You need to have the global objects outside the function when you mark them as global:

de = 0.0
ep = 0.0

def fun1():
    global de, ep
    with open("Di_Tub.csv", "r") as f3:
        reader3 = csv.reader(f3, delimiter=';')
        i3 = 0
        for row3 in reader3:
            i3 = i3 + 1
            if i3 >= 1:
                if row3[0] == DN:
                    if row3[1] == SCH:
                        de = float(row3[2])
                        ep = float(row3[3])
   # f3.close() # you don't need this, "with open" does this for you
fun1()
Di = (de - 2*ep)/1000 # this will now work
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2 Comments

@EduardSchachtSasse no problem. I am glad that I could help. If my answer helped you please mark it as the answer to your question.
Sorry, I was actually mistaken. The code ran without errors but "de" and "ep" were equal to 0 regardless of what was in the f3 file. I have tried the other answer's suggestions, which didn't work as well. Would you have any other solution?
1

You should define the variables outside the function So it should be:

            global de, ep

            def fun1():
                with open("Di_Tub.csv", "r") as f3:
                    reader3 = csv.reader(f3, delimiter=';')
                    i3 = 0
                    for row3 in reader3:
                        i3 = i3 + 1
                        if i3 >= 1:
                            if row3[0] == DN:
                                if row3[1] == SCH:
                                    de = float(row3[2])
                                    ep = float(row3[3])
                f3.close()
            fun1()
            Di = (de - 2*ep)/1000
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Comments

0

I recommend you use a return statement instead of global variables, but if you want to use global variables you should declare them outside of the function.

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