CODEWITHSUNDEEP
pythonpython-3.xoperatorseval
Lewis Hobden
Lewis Hobden

Reputation: 13

eval() with a variable operator

I'm Using Python 3.4. I receive the error:

Traceback (most recent call last):
  File "H:/GCSE's/Computing/Assesment/1/School Grading Script.py", line 44, in <module>
    if answer== eval(num1<currentop>num2):
TypeError: unorderable types: int() < str()

when trying to execute this code

operator=["+","-","*"]
num1=random.randint(0,10)
num2=random.randint(0,10)
currentop=random.choice(operator)

answer = input("What is " + str(num1) + str(currentop) + str(num2) + "?\n")
if answer== eval(num1<currentop>num2):
    print("correct")
else:
    print(incorrect)

What I want to do is to check the answer against the randomly generated variables

Upvotes: 0

Views: 1289

Answers (4)

Devansh Bansal
Devansh Bansal

Reputation: 177

Following are the list of problems in your code:

  1. eval is used with string variables.You should convert num1 and num2 as: str(num1) and str(num2).
  2. quote incorrect
  3. also your variable answer contains string type of value as input returns a string so u should cast input to int.

So after correcting all these the following code should work:

import random
operator=["+","-","*"]
num1=random.randint(0,10)
num2=random.randint(0,10)
currentop=random.choice(operator)

answer = int(input("What is " + str(num1) + str(currentop) + str(num2) + "?\n"))
if answer== eval(str(num1)+str(currentop)+str(num2)):
    print("correct")
else:
    print('incorrect')

Upvotes: 1

idjaw
idjaw

Reputation: 26600

Using eval is really bad practice, and should be avoided. For what you are trying to do, you should be making use of operator.

Change your data structure to use a dictionary to make it easier on you to perform your operations. Something like this: 

import operator

operators = {
    "+": operator.add
} 

num1 = 4
num2 = 5

res = operators.get("+")(num1, num2)

Output of res:

9

To apply your random implementation in to this, you make use of the dictionaries keys() to do a random.choice on that:

random.choice(list(operators.keys()))

Simple example applying random: 

import operator
import random

operators = {
    "+": operator.add,
    "-": operator.sub,
    "*": operator.mul
}

num1 = 4
num2 = 5

res = operators.get(random.choice(list(operators.keys())))(num1, num2)

Upvotes: 4

ergonaut
ergonaut

Reputation: 7057

You need to convert it to a string, also "Incorrect" needs to be quoted:

import random
operator=["+","-","*"]
num1=random.randint(0,10)
num2=random.randint(0,10)
currentop=random.choice(operator)

answer = input("What is " + str(num1) + str(currentop) + str(num2) + "?\n")
if answer== eval(str(num1)+str(currentop)+str(num2)):
    print("correct")
else:
    print("incorrect")

And as others have pointed out, unless for testing purposes, don't use eval.

Upvotes: 1

Avi&#243;n
Avi&#243;n

Reputation: 8395

You are mixing int, num1 and num2 and str, currentop. Cast them to str and it would work:

if answer == eval(str(num1)+currentop+str(num2)):

PS: You should avoid using eval().

Upvotes: 1

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