11.2. Importing Modules

One of the most important things to realize about modules is that they are data objects. Just like a string is a collection of individual characters, and a list is a collection of individual elements, module objects are collections of data values and Python code blocks.

11.2.1. The import Keyword

Before we can use any of the items stored in a module, we must import it. The syntax for this is:

import module_name

The import keyword tells Python to find the file called module_name and make it available for use in the program. For example, the statement import turtle creates a new name, turtle, which points to the module where all of the turtle data and functions are stored.

Warning

Put all import statements in the very first lines of a program! This avoids runtime errors by importing all module items well before your code calls for them.

To use something stored in a module, we use dot notation, which joins the name of the module with a variable or function name:

module_name.variable_name              # Access the data assigned to variable_name
module_name.function_name(arguments)   # Call function_name

For example, we have used the string module to access a list of all the lowercase letters, and we have used the turtle module to draw a circle on the screen:

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import string
import turtle

print(string.ascii_lowercase)    # Prints abcdefghijklmnopqrstuvwxyz
turtle.circle(50)                # Draws a circle with a 50 pixel radius

We can read these two examples of dot notation like this:

  1. Line 4 - In the string module, access the value for the variable ascii_lowercase.
  2. Line 5 - In the turtle module, call the function called circle, and send it the argument 50.

Note

In order to call a function stored in a module, we MUST know the name of that function. To access a data value stored in a module, we MUST know the variable name for that value.

11.2.1.1. Find the Names of Module Items

To figure out the names of all the items stored in a module, we could look them up with a Google search. However, Python has a useful directory function, dir(), that returns a list of names for everything stored in a module.

Example

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import string

print(dir(string))

Console Output

['Formatter', 'Template', '_ChainMap', '_TemplateMetaclass', '__all__', '__builtins__',
'__cached__', '__doc__', '__file__', '__loader__', '__name__',
'__package__', '__spec__', '_re', '_sentinel_dict', '_string',
'ascii_letters', 'ascii_lowercase', 'ascii_uppercase', 'capwords', 'digits',
'hexdigits', 'octdigits', 'printable', 'punctuation', 'whitespace']

To make this output easier to read, we can use a loop to print the list one element per line.

Tip

From the list of names, skip those that begin with underscores __. Using these is a more advanced skill, and we will focus on the other options for now.

11.2.2. The from Keyword

The import keyword makes every data value and function in a module available for use. However, if we only need a few of the items from a module, we can use the from keyword to import only those items.

from module_name import item_name

item_name refers to the specific function or variable that we want from the module. If we want to import more than one item, we separate the names by commas.

Example

Compare the syntax and results from the following imports:

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import string

print(string.punctuation)
print(string.ascii_letters)

Console Output

!"#$%&'()*+,-./:;<=>[email protected][\]^_`{|}~
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

Adding the from keyword:

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from string import punctuation

print(punctuation)
print(ascii_letters)

Console Output

!"#$%&'()*+,-./:;<=>[email protected][\]^_`{|}~
Traceback (most recent call last):
File "main.py", line 4, in <module>
   print(ascii_letters)
NameError: name 'ascii_letters' is not defined

Note that when we combine from ... import, we do NOT need to use dot notation. We can call the variable or function directly by its name. Also note that ascii_letters results in a NameError, because that data was not imported from the string module in line 1.

11.2.3. The as Keyword

Python gives us a way to rename the items we import by including the as keyword as part of the import statement:

import module_name as new_name
from module_name import item_name as new_name

11.2.4. Try It!

  1. Using the clues in the code below, import the modules required to make the program work:

    Challenge: Modify the code to replace one import statement with from module_name import function_name.

  2. Using the clues in the code below, rename the turtle module to make the code work: