The docstring of the adder() function shown below contains two examples of how to use the function. The function resides in a file named example.py. Use the doctest module to test the examples in this docstring.
# This function resides in a file named example.py
def adder(x, y):
"""
Add two numbers.
Parameters
----------
x : int or float
First number.
y : int or float
Second number.
Returns
-------
z : int or float
The result of adding two numbers.
Example
-------
>>> adder(1, 2)
3
>>> adder(1.5, 8)
9.5
"""
z = x + y
return z
Running doctest on the example produces the following output:
$ python -m doctest -v example.py
Trying:
adder(1, 2)
Expecting:
3
ok
Trying:
adder(1.5, 8)
Expecting:
9.5
ok
1 items had no tests:
example
1 items passed all tests:
2 tests in example.adder
2 tests in 2 items.
2 passed and 0 failed.
Test passed.
This docstring imports NumPy where it is used to add two arrays.
# This function resides in a file named example.py
def array_adder(x, y):
"""
Add two arrays.
Parameters
----------
x : ndarray
First array.
y : ndarray
Second array.
Returns
-------
z : ndarray
The result of adding two arrays.
Example
-------
>>> import numpy as np
>>> a = np.array([1, 2, 3])
>>> b = np.array([5, 6, 7])
>>> array_adder(a, b)
array([ 6, 8, 10])
"""
z = x + y
return z
$ python -m doctest -v example.py
Trying:
import numpy as np
Expecting nothing
ok
Trying:
a = np.array([1, 2, 3])
Expecting nothing
ok
Trying:
b = np.array([5, 6, 7])
Expecting nothing
ok
Trying:
array_adder(a, b)
Expecting:
array([ 6, 8, 10])
ok
1 items had no tests:
example
1 items passed all tests:
4 tests in example.array_adder
4 tests in 2 items.
4 passed and 0 failed.
Test passed.
Gavin Wiggins © 2025.
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