Defining and Using Python Functions

The first few tasks require us to create the split_names function to take a string and split it into the first and last name, returning a dictionary with the first_name and last_name keys.

We'll modify the function to get each of the assert statements that utilize this, so let's write the implementation to get the initial assertion to succeed:

testing-functions.py

# 1) Write a `split_name` function that takes a string and returns a dictionary with first_name and last_name

def split_name(name):
    names = name.split()
    first_name = names[0]
    last_name = names[-1]
    return {
        'first_name': first_name,
        'last_name': last_name,
    }

assert split_name("Kevin Bacon") == {
    "first_name": "Kevin",
    "last_name": "Bacon",
}, f"Expected {{'first_name': 'Kevin', 'last_name': 'Bacon'}} but received {split_name('Kevin Bacon')}"

Now when we run the file again we'll see the next error:

$ python3.7 testing-functions.py
Traceback (most recent call last):
  File "testing-functions.py", line 19, in <module>
    }, f"Expected {{'first_name': 'Victor', 'last_name': 'Von Doom'}} but received {split_name('Victor Von Doom')}"
AssertionError: Expected {'first_name': 'Victor', 'last_name': 'Von Doom'} but received {'first_name': 'Victor', 'last_name': 'Doom'}

This test shows that our initial implementation doesn't handle having multiple spaces in the initial name. Thankfully, to get around this, we can assume that we only need to split on the first space in the string. This is something that we can do with the str.split function by passing an additional argument with the number of splits to perform.

testing-functions.py (partial)

# 1) Write a `split_name` function that takes a string and returns a dictionary with first_name and last_name

def split_name(name):
    first_name, last_name = name.split(maxsplit=1)
    return {
        'first_name': first_name,
        'last_name': last_name,
    }

assert split_name("Kevin Bacon") == {
    "first_name": "Kevin",
    "last_name": "Bacon",
}, f"Expected {{'first_name': 'Kevin', 'last_name': 'Bacon'}} but received {split_name('Kevin Bacon')}"

# 2) Ensure that `split_name` can handle multi-word last names

assert split_name("Victor Von Doom") == {
    "first_name": "Victor",
    "last_name": "Von Doom",
}, f"Expected {{'first_name': 'Victor', 'last_name': 'Von Doom'}} but received {split_name('Victor Von Doom')}"

Running the tests again, we shouldn't see any more errors related to split_name.

A palindrome is a word that reads the same from right to left as it does from left to right (or reversed). An example is 'radar'. The word 'radar' reversed is still 'radar'. We need to create a function called is_palindrome that takes a string and checks to see if it matches itself in reverse. The simplest way that we can do this is by using slicing to reverse the string:

testing-functions.py (partial)

# 3) Write an `is_palindrome` function to check if a string is a palindrome (reads the same from left-to-right and right-to-left)

def is_palindrome(item):
    return item == item[::-1]

assert is_palindrome("radar") == True, f"Expected True but got {is_palindrome('radar')}"
assert is_palindrome("stop") == False, f"Expected False but got {is_palindrome('stop')}"

# 4) Make `is_palindrome` work with numbers

assert is_palindrome(101) == True, f"Expected True but got {is_palindrome(101)}"
assert is_palindrome(10) == False, f"Expected False but got {is_palindrome(10)}"

This will get #3 to succeed, but when we hit the assertions under #4 we'll see the following errors:

$ python3.7 testing-functions.py
Traceback (most recent call last):
  File "testing-functions.py", line 31, in <module>
    assert is_palindrome(101) == True, f"Expected True but got {is_palindrome(101)}"
  File "testing-functions.py", line 23, in is_palindrome
    return item == item[::-1]
TypeError: 'int' object is not subscriptable

We can fix this by type casting our item parameter to be a string before we make our comparison. This will also make it work with floats like 1.1:

testing-functions.py (partial)

# 3) Write an `is_palindrome` function to check if a string is a palindrome (reads the same from left-to-right and right-to-left)

def is_palindrome(item):
    item = str(item)
    return item == item[::-1]

assert is_palindrome("radar") == True, f"Expected True but got {is_palindrome('radar')}"
assert is_palindrome("stop") == False, f"Expected False but got {is_palindrome('stop')}"

# 4) Make `is_palindrome` work with numbers

assert is_palindrome(101) == True, f"Expected True but got {is_palindrome(101)}"
assert is_palindrome(10) == False, f"Expected False but got {is_palindrome(10)}"

The build_list function is going take an item and the number of times to add it to a list that it will return. Based on the second assertion that we can see in the file, the count should also have a default value of 1.

Let's write a function to build a range, then loop through it and append the item to a list that we'll return at the end of the function.

testing-functions.py (partial)

# 5) Write a `build_list` function that takes an item and a number to include in a list

def build_list(item, count=1):
    items = []
    for _ in range(count):
        items.append(item)
    return items

assert build_list("Apple", 3) == [
    "Apple",
    "Apple",
    "Apple",
], f"Expected ['Apple', 'Apple', 'Apple'] but received {repr(build_list('Apple', 3))}"
assert build_list("Orange") == [
    "Orange"
], f"Expected ['Orange'] but received {repr(build_list('Orange'))}"

If we get no output when we run the script now, then we've successfully written functions that show we understand how functions are constructed and can leverage other language features like conditionals and loops.