Skipping every other element after the first

Question

I have the general idea of how to do this in Java, but I am learning Python and not sure how to do it.

I need to implement a function that returns a list containing

Answer 1

Or you can do it like this!

    def skip_elements(elements):
        # Initialize variables
        new_list = []
        i = 0

        # Iterate through the list
        for words in elements:

            # Does this element belong in the resulting list?
            if i <= len(elements):
                # Add this element to the resulting list
                new_list.append(elements[i])
            # Increment i
                i += 2

        return new_list

    print(skip_elements(["a", "b", "c", "d", "e", "f", "g"])) # Should be ['a', 'c', 'e', 'g']
    print(skip_elements(['Orange', 'Pineapple', 'Strawberry', 'Kiwi', 'Peach'])) # Should be ['Orange', 'Strawberry', 'Peach']
    print(skip_elements([])) # Should be []

Answer 2

items = range(10)
print items
>>> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
print items[1::2] # every other item after the second; slight variation
>>> [1, 3, 5, 7, 9]
]

Answer 3

Slice notation a[start_index:end_index:step]

return a[::2]

where start_index defaults to 0 and end_index defaults to the len(a).

Answer 4

def skip_elements(elements):
    # Initialize variables
    new_list = []
    i = 0

    # Iterate through the list
    for words in elements:
        # Does this element belong in the resulting list?
        if i <= len(elements):
            # Add this element to the resulting list
            new_list.insert(i,elements[i])
        # Increment i
        i += 2

    return new_list

Answer 5

There are more ways than one to skin a cat. - Seba Smith

arr = list(range(10)) # Range from 0-9

# List comprehension: Range with conditional
print [arr[index] for index in range(len(arr)) if index % 2 == 0]

# List comprehension: Range with step
print [arr[index] for index in range(0, len(arr), 2)]

# List comprehension: Enumerate with conditional
print [item for index, item in enumerate(arr) if index % 2 == 0]

# List filter: Index in range
print filter(lambda index: index % 2 == 0, range(len(arr)))

# Extended slice
print arr[::2]

Answer 6

b = a[::2]

This uses the extended slice syntax.