Method of Accepting User Input and eval Function

Most real programs need to react to information supplied by the person running them. Python makes this easy with the built-in input() function, which pauses the program and waits for the user to type something.

The input() Function

The input() function displays an optional prompt and always returns whatever the user types as a string.

name = input("Enter your name: ")
print("Hello,", name)

Converting Input to Other Data Types

Since input() always returns a string, you need to convert it explicitly if you want to work with numbers.

age = int(input("Enter your age: "))
height = float(input("Enter your height in meters: "))
print(age + 1)

The eval() Function

The eval() function goes a step further than simple conversion. It takes a string and evaluates it as if it were a Python expression, which is useful when a user might enter a calculation rather than a single value.

expression = input("Enter an expression: ")
result = eval(expression)
print("Result:", result)

Coming Up

Now that you can gather input while a program runs, the next topic covers how to work with data stored outside your program, using Python's file input and output functions.