Libraries & Methods I have used.

Regular expression

re {file: regexp} {usecases: [match string, add matches to a list or dictionary]}

File system traversal

os, os.path: isfile, isdir, join

External programs

subprocess

Date time parsing for timeseries

calendar datetime: datetime, timedelta

Data structures and keywords (tag code)

list {file: list} {usecases: [create a numerical range with start end & step, search for element, append remove or insert in position, iterate (optional with index), minimum or maximum value, sort, filter numerical range, sum, method on each element, string split to create a list, list joined to a string] tuple {files: /tuple/} {usecases: input space separated string to tuple}
dictionary {file: dict, count occurrences} {usecases: [look up a key's values or keys with same value, count occurrences of element, traverse a dict of lists, unique elements (set)}

if, for, while

Printing strings & numbers

%d, %g {file: print string or integer, count occurrences} {usecases: mix integers and strings) round, format %s {usecases: substring, remove spaces & linebreaks}

writing to files

open, write, close {file: file write read} {usecases: write string, write list elements}

Boolean logic

boolean truth tables for statements (if, or, and)