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Input validation

You do absolutely no input validation when the user enters an integer. If the user enters a non-integer value, like foo, or bar, your code will crash with a ValueError. The correct way to obtain user input is to use a try/except block, like this:

try:
 var1 = int(input( ... ))
 var2 = int(input( ... ))
 ...
except ValueError:
 print("Invalid input!")
 ... 

By doing this, you can be sure that your program won't crash on invalid input.

Input mappings

Right now, you're chaining if/elif/else statements to check user input. This is not an optimal way to do this. Rather, you can create a dictionary mapping, like the below, for possible inputs:

OPERATIONS = {
 "+": add,
 "-": sub,
 ...
}

Then, all you have to do to get, and run user input is something like this:

operation = input( ... )
if operation in OPERATIONS:
 OPERATIONS[operation](var1, var2)
else:
 print("Invalid operation!")

This makes your code much clearer, and easier to read, rather than a chain of if/elif/else statements.

Use math and operator

There is absolutely no reason to define your own mathematical functions, just so you can use them in a dictionary mapping, you should be using the math and operator modules instead. These all provide built-in functions, like add, and sub, or values, like \$\pi\$ or \$e\$.

General nitpicks

• There's no need for parentheses around if/elif/else statements. They can be written like this:

   if condition:
   ...
  

• You should be using an if __name__ == "__main__" guard. This ensures that if your code is imported to another file, certain code will not be run. This means that this function call right here:

   main()
  

  Should become this:

   if __name__ == "__main__":
   main()
  

• There's no need to import math twice. Once it's imported, it's functions and variables already populate the file's namespace.

• Finally, if you're going to write comments for your functions (in this case your comments are fairly useless), you should be using docstrings instead. A typical docstring looks something like this:

   def my_func( ... ):
   """Brief description.
   More detailed description.
   Keyword arguments:
   argument -- Argument description.
   """
   ...
  

  Keep in mind though, if your code is self-commenting, and clearly written, the comments probably aren't needed.