Palindrome file search

2022-01-25.py

question = """
You are given three files named first_page.txt, second_page.txt, and third_page.txt 
with the occurrence of at least one palindrome in each of them. Write a script to find the following:

The exact number of palindromes in each file.
The line numbers of the palindromes in each file.
"""

import re

# originally from 2021-08-16: Palindrom Hunt

def palTest(pal, str):
    pal_double = re.compile(r'((.)' + pal + r'(\2))')
    pal_single = re.compile(r'((.)' + pal + r'(\2))')
    double_test = pal_double.search(str)
    if double_test:
        if str == pal:
            print('equal')
            return double_test.group(1)
        else:
            return double_test.group(1)

    else:
        single_test = pal_single.search(str)
        if single_test:
            print('single')
            return single_test.group(1)
        else:
            return False

def pSubstring(input):
    pals = {}

    out = palTest('', input)

    # start with double center
    while out:
        next = palTest(out, input)
        if out == input:
            break
        if next:
            out = next
        else:
            break
    if out:
        pals[out] = 1

    for char in input:
        out = palTest(char, input)
        if out:
            pals[out] = 1

    for pal in pals.keys():
        if pal and len(pal) >= 4:
            return(pal)

filenames = [ './2022/first_page.txt', './2022/second_page.txt', './2022/third_page.txt']
for filename in filenames:
    with open(filename, newline='') as lines:
        palindrome_count = 0
        linenbr = 0
        for line in lines:
            linenbr += 1
            palindrome = pSubstring(line)
            if palindrome:
                palindrome_count += 1
                print(filename + ":" + str(linenbr) + " " + palindrome)
    print(filename + " has " + str(palindrome_count) + " palindrome(s)")