Primitives

isnone(x)

Checks if x is None. Handy with filtering functions:

remove(isnone, list_of_dirty_data)

Plays nice with silent(), which returns None on fail:

remove(isnone, imap(silent(int), strings_with_numbers))

Note that it’s usually simpler to use keep() or compact() if you don’t need to distinguish between None and other falsy values.

notnone(x)

Checks if x is not None. A shortcut for complement(isnone) meant to be used when bool is not specific enough. Compare:

select_values(notnone, data_dict) # removes None values
compact(data_dict)                # removes all falsy values
inc(x)

Increments its argument by 1.

dec(x)

Decrements its argument by 1.

even(x)

Checks if x is even.

odd(x)

Checks if x is odd.