micgeronimo - 1 year ago 118
Python Question

# Split string of digits into lists of even and odd integers

Having such code

``````numbers = '1 2 3 4 5 6 7 8'
nums = {'evens': [], 'odds': []}

for number in numbers.split(' '):
if int(number) % 2:
nums['odds'].append(number)
else:
nums['evens'].append(number)
``````

How can accomplish same on fewer lines?

Short code is not better code. Short code is not faster code. Short code is not maintainable code. Now, that said, it is good to make your individual components concise and simple.

Here's what I would do:

``````def split_odd_even(number_list):
return {
'odds': filter(lambda n: (n % 2) != 0, number_list),
'evens': filter(lambda n: (n % 2) == 0, number_list)
}

def string_to_ints(string):
return map(int, numbers.strip().split())

numbers = '1 2 3 4 5 6 7 8 9 10'
nums = split_odd_even(string_to_ints(numbers))

print nums
``````

This gives me:

``````{'odds': [1, 3, 5, 7, 9], 'evens': [2, 4, 6, 8, 10]}
``````

While this code has actually added a few lines in length, it has become much more clear what the program is doing, as we've applied Abstraction and made each component of the code do only one thing well.

Even though we've added two functions, the most-visible part of the code has gone from this:

``````numbers = '1 2 3 4 5 6 7 8'
nums = {'evens': [], 'odds': []}
for number in numbers.split(' '):
if int(number) % 2:
nums['odds'].append(number)
else:
nums['evens'].append(number)
``````

To this:

``````numbers = '1 2 3 4 5 6 7 8 9 10'
nums = split_odd_even(string_to_ints(numbers))
``````

And just by reading these two lines, we know that `numbers` is converted from a string to a list of `int`s, and that we then split those numbers into odd and even, and assign the result to `nums`.

To explain a a couple of things that may not be familiar to all:

• `map()` calls a function for every item in a `list` (or `tuple` or other iterable), and returns a new list with the result of the function being called on each item. In this case, we use it to call `int()` on each item in the list.

• `filter()` calls a function for every item in a `list` (or `tuple` or other iterable), which returns `True` or `False` for each item (well, truthy or falsey), and returns a list of items that evaluated to `True` when the function is called.

• Lambda Expressions (`lambda`) are like "mini-functions" that take arguments and can be created in-place.

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download