# 5.15 Other Sequence Processing Functions¶

### Finding the Minimum and Maximum Values Using a Key Function¶

In [1]:

    'Red' < 'orange'

Out[1]:

    True

- `'R'` “comes after” `'o'` in the alphabet, so you might expect `'Red'` to be less than `'orange'` and the condition above to be `False`.
- Strings are compared by their characters’ underlying numerical values, and lowercase letters have higher numerical values than uppercase letters.
- Confirm with built-in function `ord`:

In [2]:

    ord('R')

Out[2]:

    82

In [3]:

    ord('o')

Out[3]:

    111

In [4]:

    colors = ['Red', 'orange', 'Yellow', 'green', 'Blue']

- Assume that we’d like to determine the minimum and maximum strings using alphabetical order.
- Can specify sort order with the `key` argument.

In [5]:

    min(colors, key=lambda s: s.lower())

Out[5]:

    'Blue'

In [6]:

    max(colors, key=lambda s: s.lower())

Out[6]:

    'Yellow'

### Iterating Backwards Through a Sequence¶

In [7]:

    numbers = [10, 3, 7, 1, 9, 4, 2, 8, 5, 6]

In [8]:

    reversed_numbers = [item ** 2 for item in reversed(numbers)]

In [9]:

    reversed_numbers

Out[9]:

    [36, 25, 64, 4, 16, 81, 1, 49, 9, 100]

### Combining Iterables into Tuples of Corresponding Elements¶

- Built-in function `zip` enables you to iterate over multiple iterables of data at the same time.
- Receives any number of iterables and returns an iterator that produces tuples containing the elements at the same index in each.

In [10]:

    names = ['Bob', 'Sue', 'Amanda']

In [11]:

    grade_point_averages = [3.5, 4.0, 3.75]

In [12]:

    for name, gpa in zip(names, grade_point_averages):
        print(f'Name={name}; GPA={gpa}')

    Name=Bob; GPA=3.5
    Name=Sue; GPA=4.0
    Name=Amanda; GPA=3.75

- Shortest argument determines the number of tuples produced.

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