Introduction

This is as an "extension" of the python itertools builtin library.
It defines a list of additional utility functions for efficient iteration (some of them are defined also in the "recipes" section of the itertools documentation page)

Prerequisites & installation

This library is written in Python >= 3.5 and dont have any external dependencies

Install it via setup.py script

git clone https://github.com/Vykstorm/more-itertools.git
cd more-itertools
python setup.py install

Examples

from itertools import *
from moreitertools import *
from random import randrange
from operator import lt

# Find the first number greater than zero
first_true([-1, 2, 0, -3, 4], pred=lambda x: x > 0) # 2

# Count the amount of non zero elements
quantify([0, 10, 2, 0, 3, 1]) # 4

# Repeat a sequence 2 times
ncycles(range(0, 3), 2) # 0, 1, 2, 0, 1, 2

# Prepend and element to a sequence
prepend(0, range(10, 13)) # 0, 10, 11, 12

# Get a iterator that returns the items in a string
# without duplicates and preserving the order in which they appear
unique_everseen('BCADABCE') # 'B','C','A','D','E'

# Execute a function n times
repeatfunc(randrange, 4, start=0, stop=10) # 7, 0, 5, 6

# Search the last item in a sequence higher than the previous one
X = [4, 0, 0, -1, 4, 3, 5, 1]
last_true(starmap(lambda x, y: y if y > x else 0, pairwise(X))) # 5

There is additionaly a useful tool called debugiter that will help you debugging your code when working with complex iterators:

from moreitertools import *

# Returns even numbers multiplied by 2 and odd multiplied by 3
it = roundrobin(
    map(lambda x: x * 2, range(0, 100, 2)),
    map(lambda x: x * 3, range(1, 100, 2))
)
print(debugiter(it))

The output will be:

0, 3, 4, 9, 8, 15, 12, 21, 16, 27, ..., 285, 192, 291, 196, 297  (100 items in total)

debugiter will show part of the content and the number of items inside the iterator

Also you can interactively debug the iterator while iterating over it:

it = debugiter(range(0, 60, 3))
print(it)
print('Next item is: ', next(it))
print(it)
print('Next item is: ', next(it))
print(it)

Output:

0, 3, 6, 9, 12, 15, 18, 21, 24, 27, ..., 45, 48, 51, 54, 57  (20 items in total)
Next item is 0
3, 6, 9, 12, 15, 18, 21, 24, 27, 30, ..., 45, 48, 51, 54, 57  (19 items in total)
Next item is 3
6, 9, 12, 15, 18, 21, 24, 27, 30, 33, ..., 45, 48, 51, 54, 57  (18 items in total)

Documentation

To list all avaliable functions in this module, you can execute the next:

python -c "import moreitertools; print(dir(moreitertools))"

Issue the command help or access the docstrings of the functions to get usage information:

from moreitertools import *
help(first_true)
print(pairwise.__doc__)