Wrapping iterators in generators in generators in ...

generators_of_generators.py

# remove pesky trailing newlines from iterating over a text file

def denewlining(line_iterator):
    for line in line_iterator:
        yield line.rstrip("\n\r")


with open(__file__) as infile:
    for line in denewlining(infile):
        print(f"{line!r} <-- look ma! no trailing newlines!")
print()


# clip to read only 'n' lines

def clipping(n, seq):
    for _, line in zip(range(n), seq):
        yield line


with open(__file__) as infile:
    for i, line in enumerate(clipping(5, denewlining(infile)), start=1):
        print(f"{i} {line!r} <-- look ma! no trailing newlines!")
print()


# collapse repeated lines (import repeated intentionally for demonstration)

import itertools
import itertools
def collapse_repeaters(seq):
    for line, _ in itertools.groupby(seq):
        yield line


with open(__file__) as infile:
    for line in collapse_repeaters(denewlining(infile)):
        print(f"{line!r} <-- look ma! no trailing newlines!")