Working With Iterables

Aggregate and Analyze Iterables

This tutorial recaps what we've learned about Python iterables, such as strings and lists. We'll use built-in functions like min(), max(), and sum() to extract information from these iterables.

Let's talk about iterables.

An iterable is a Python object that can be iterated over, meaning you can traverse through all the elements in the object.

You already know the most common Python iterables: strings, lists, and tuples:

str = 'iterable'
lst = [1, 2, 3]
tpl = (1, 2, 3)
dict = {'a': 1, 'b': 2, 'c': 3}

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Remember that you can loop through the elements in all of these iterables:

def traverse(iter):
  for item in iter:
    print(item)

traverse('iter')
traverse([1, 2, 3])
traverse((1, 2, 3))
traverse({'a': 1, 'b': 2, 'c': 3})

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Output

Sometimes, you'll need to get some general information about these iterables.

For example, you might want to get the maximum value of a list of numbers.

You could do this using a for-loop:

numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
max_value = 0
for number in numbers:
    if number > max_value:
        max_value = number
print('The maximum value is:', max_value)

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Output

While this approach works, it involves quite a bit of code. Fortunately, Python offers built-in functions that can simplify these tasks significantly.

The max() function returns the largest item in an iterable.

Here's how you can use it:

numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
max_value = max(numbers)
print('The maximum value is:', max_value)

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Output

Similarly, the min() function returns the smallest item in an iterable.

numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
min_value = min(numbers)
print('The minimum value is:', min_value)

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Output

If we apply min() and max() to a string, we get the smallest and largest character based on their Unicode values.

This behavior can be useful when you want to find the 'smallest' or 'largest' character in a string based on alphabetical order.

Let's see how this works:

text = 'hello'
 
print('The minimum character is:', min(text))
print('The maximum character is:', max(text))

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Output

Now, let's test your understanding!

What will be the output?

nums = [10, 5, 20]
min_num = min(nums)
max_num = max(nums)
print(min_num, max_num)

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What will be the output?

text = 'abc'
min_char = min(text)
max_char = max(text)
print(min_char, max_char)

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The sum() function returns the sum of all items in an iterable, such as a list of numbers.

Here's how you can use it:

numbers = [1, 2, 3, 4, 5]
total = sum(numbers)
print('The total sum is:', total)

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Output

However, while min() and max() work with strings, the sum() function is only for numerical iterables.

What will be the output?

numbers = (2, 4, 6, 8)
total = sum(numbers)
print(total)

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What will be the output?

mixed_values = [1, 'two', 3]
max_value = max(mixed_values)
print(max_value)

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