Split a program

greetings.py defines greet. main.py imports it and calls it. The check runs greetings.py. main.py stays as the lesson wrote it, so you can read the import while you write the function.

A file name here is one segment, such as greetings.py. Do not write a slash or .. in the name.

Two jobs, two files

A program grows clearer when each file has one job.

• greetings.py defines the function. It does not need to print.
• main.py uses the function. It imports the name and prints the result.

The second file does not copy the function. It loads the name with from greetings import greet. The word before import is the module: the file name without .py. The word after import is the name defined in that file. The modules tutorial describes this form.

from greetings import greet
print(greet("Ada"))

If greet returns "Hello, " + name, that call prints Hello, Ada.

A worked example

Suppose the greeting should be the word Hello, a comma, a space, and the name. Build that string with +.

1. Open greetings.py.
2. Define greet with one parameter, name.
3. Return "Hello, " + name. The space after the comma is part of the string.
4. Leave main.py as it is. It already imports greet and calls greet("Ada").

def greet(name):
    return "Hello, " + name

Trace that definition with the call from main.py. The parameter name is "Ada". The return value is "Hello, Ada". print shows that string. Nothing in the function deletes a file. An import reads a module.

The comma and the space both belong inside the string, before the +.

def greet(name):
from greetings import greet

    return "Hello, " + name

return name

print(greet("Ada"))

def greet(name):

Exercise

Write greet in greetings.py. It takes a name and returns Hello, a space, and that name. Do not change main.py.

def greet(name):
    return ""

Output