How do I do simple user input in python? [duplicate]

Question

I'm just playing with input and variables. I'm trying to run a simple function:

slope = (y2-y1)/(x2-x1)

I'd like to prompt the user to enter y2, y1, x2 and x1. What is the simplest, cleanest way to do this?

Answer 1

You can use the input() function to prompt the user for input, and float to convert the user input from a string to a float:

x1 = float(input("x1: "))
y1 = float(input("y1: "))
x2 = float(input("x2: "))
y2 = float(input("y2: "))

If you're using python 2, use raw_input() instead.

Answer 2

This is the simplest way:

 x1 = float(raw_input("Enter x1: "))

Note that the raw_input() function returns a string, which is converted to a floating point number with float(). If you type something other than a number, you will get an exception:

>>> float(raw_input())
a
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
ValueError: invalid literal for float(): a

If you're using Python 3 (it sounds like you are), use input instead of raw_input.