NameError : name "a" is not defined

Question

I have made a simple calculator.py program in Python, but the program fails with NameError: "a" is not defined.

How can I fix it?

import math
def control(a, x, y, z, k):
    return {
        'ADDITION': addition(x, y),
        'SUBTRACTION': subtraction(x, y),
        'MULTIPLICATION': multiplication(x, y),
        'DIVISION': division(x, y),
        'MOD': modulo(x, y),
        'SECONDPOWER': secondPower(x),
        'POWER': power(x, y),
        'SECONDRADIX': secondRadix(x),
        'MAGIC': magic(x, y, z, k)
    }[a]
def addition(x, y):
    return float(x) + float(y)
def subtraction(x, y):
    return float(x) - float(y)
def multiplication(x, y):
    return float(x) * float(y)
def division(x, y):
    return float(x) / float(y)
def modulo(x, y):
    return float(x) % float(y)
def secondPower(x):
    return math.pow(float(x),2.0)
def power(x, y):
    return math.pow(float(x),float(y))
def secondRadix(x):
    return math.sqrt(float(x))
def magic(x, y, z, k):
    l = float(x) + float(k)
    m = float(y) + float(z)
    return (l / m) + 1.0
try:
    control(a, x, y, z, k)
except ValueError:
    print("This operation is not supported for given input parameters")
out = control(a, x, y, z, k)
print(out)

Traceback (most recent call last):
    control(a, x, y, z, k)
NameError: name 'a' is not defined

Asked By: Husni Salax

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Source

Answer 1

That’s because before you run control in the try loop, you’ve never assigned ‘a’ to anything. Try assigning something to ‘a’ right before running control.

try:
    control(a, x, y, z, k)

Answered By: MHardwick

Answer 2

You need to assign values not just to the variable a but also to other variables x, y, z, and k which you’re passing here -> control(a, x, y, z, k)

# for example:
a= 'ADDITION'
x= 1
y= 2
z=3
k=4
# and then you can call the function
control(a, x, y, z, k)

and the value of the variable a must be one of these(as you’ve defined)

'ADDITION'
'SUBTRACTION'
'MULTIPLICATION'
'DIVISION'
'MOD'
'SECONDPOWER'
'POWER'
'SECONDRADIX'
'MAGIC'

any other value of a will through a "KeyError"

Answered By: Ajeet Verma

NameError : name "a" is not defined

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