import os
import os.path
# I use "directory" for what you might call a "folder"
# For floating point numbers, use close_enough(a,b) instead
# of a == b to avoid floating-point error nightmares.
# try testing your code in the main routine.
def close_enough(a,b):
    """prec: a, b are floating-point numbers
    postc:  tells if a and b are nearly equal"""
    return abs(a - b) < 1e-6
def extract_numbers(table_row):
    """prec:  table_row is a string containing an HTML5 table
    row with integer data, which looks like this 
    <tr><td>56</td><td>45</td><td>22</td></tr>
    (It can have arbitrarily many elemnts)
    postc: returns a list with the number in it. For the
    example that'd be [56, 45, 22].  Make sure they are
    numbers and not numeric strings"""
    pass
def approximate_average(f, a, b, n):
    """prec: f is a numeric function defined on the interval [a,b]
    a < b, and n is a positive integer
    postc: returns the average of f evaluated at n + 1
    equally-spaced points in [a,b]"""
    pass
def find_arithmetic_sequence(num_list, k):
    """prec:  num_list is a list of numbers
    postc: returns True if num_list contains an arithmetic 
    progression length at least k
    example find_arithmetic_sequence([4,2,7,9,11,3,5], 3 -> True
    becaue 7, 9, 11 is an arithmetic sequence.
    """
    pass
def contains(search_string, file_name):
    """prec: search_string is a string
    file_name is an existing file
    post:  returns True if the file contains the seach string"""
    pass
def grip(search_string, file_name):
    """prec: search_string is a string
    file_name is a file name (that exists)
    postc:  prints out all lines in the file containing
    the search string"""
    pass
def make_a_list(file_name):
    """prec:  file_name is an existing file containing 
    space-separated rows of numbers.
    postc: returns a list of the numbers in the file
    in the order in which they are present"""
def transform(file_name, old, new):
    """prec: file_name is an existing file
    old, new are strings.
    postc: produces a file with the name file_name + ".out"
    in which the contents of file_name have every instance
    of the string out replaced with the string new"""
def spill(some_directory):
    """prec: some_directory is an existing directory
    postc:  returns a list of the regular files in 
    that direcory."""
def list_contents(some_directory):
    """prec: some_directory is a possibly existing directory.
    post: returns False if some_directory is a regular file
    or if some_directory does not exist.
    postc:  returns a list of the regular files (not directories)
    in the directory otherwise"""
    pass