subject : Theory of Computing

A .py file as your answer to question 2.

Func_headers-M1.py

import re

# '$' isn't allowed in Python variable names #Python variable names must start with a letter or a '_'... start_var_chars = '[a-zA-Z_]' #... but digits are also allowed in trailing chacters trail_var_chars = '[a-zA-Z0-9_]' var_chars = start_var_chars + trail_var_chars + '*'

#Verbose regex definition #Some notes on Python string literal syntax # 1. A triple-quoted string, delimited by ''' or """, is allowed to span # multiple lines in the source file. # # 2. The 'r' string defintion prefix stands for 'raw', and means that the # backslash characters are passed to the regular expression engine # without interpretation. # # 3. The f string defintion prefix allows for inserting variables # into the string by enclosing them in curly braces. For # example, {var_chars} #

#FOR THE MIDTERM, ENHANCE THIS REGULAR EXPRESSION ACCORDING TO THE INSTRUCTIONS func_header_regex =\ re.compile(fr'''^\s* # any and all blanks & tabs at start of string def\s+ # "def" then blanks & tabs {var_chars} # function name \s*\(\s* # blanks & tabs, '(', blanks & tabs {var_chars} , #parameter name *\s*\)\s*:\s*$ # blanks & tabs, ')', blanks & tabs, ':' # blanks & tabs, end of string ''', re.VERBOSE)

def Match_func_header(text): #FOR THE MIDTERM, MODIFY THE RETURN SO THAT THIS FUNCTION ONLY RETURNS THE # FUNCTION HEADER, OMITTING ENCLOSING WHITE SPACE. return func_header_regex.search(text)

if __name__ == '__main__': o = open('func_headers.out','w') while True: filename = input('Enter file to check for function headers, or enter to quit: ') if filename == '': break try: f = open(filename, 'r') except: print(f'Could not open "{filename}" for reading') continue print(f'Looking for function headers in "{filename}" ', file=o) lineNum = 1 for line in f.readlines(): #THE PROCESSING BELOW DEPENDS ON Match_func_header RETURNING A MATCH # OBJECT, WHICH WILL NOT NECESSARILY BE TRUE AFTER YOU MAKE YOUR # MODIFICATIONS m = Match_func_header(line) #IN THE PROCESSING BELOW, THE "[:-1]" AT THE END OF THE OUTPUT # STRING JUST REMOVES THE TRAILING NEWLINE CHAR. THAT MAY NO LONGER # BE NEEDED AFTER YOU MAKE YOUR MODIFICATIONS if m: pfx = 'Python function header on line' print(f'{pfx} {lineNum}: "{m.group()[:-1]}"', file=o) else: pfx = 'No Python function header on line' print(f'{pfx} {lineNum}: "{line[:-1]}"', file=o) lineNum += 1

print(f' "{filename}" function header search complete ', file=o) f.close() print('Function header detection testing complete.') o.close()

2. (40 points) Modify the file Func_headers.py, available on iLearn, so that the program shows function headers it detects in an input file. The most important change you will need to make is to func_header_regex, so that in addition to matching function headers with single parameters: It allows that single parameter to take a default value of an integer, a string, or a variable. It captures the function header match in a group, excluding leading and trailing white space. You must also change Match_func_header, so that it returns the matched header without the enclosing white space. Match_func_header must still return None if there is no match. Here are some examples of matched and unmatched lines: Matched lines Unmatched lines def f(a): def f(): def f (a) : def if (a): def f12_(a5b): def f12_(a5b) def f(a=12): def f(a=3.14): def f(a=-12): def f(a=12-): def f(a='hello world'): def f('hello world'): def f(a="test"): def f(a="test): def f(a=fileName) : def f(a=2 fileName) : 2. (40 points) Modify the file Func_headers.py, available on iLearn, so that the program shows function headers it detects in an input file. The most important change you will need to make is to func_header_regex, so that in addition to matching function headers with single parameters: It allows that single parameter to take a default value of an integer, a string, or a variable. It captures the function header match in a group, excluding leading and trailing white space. You must also change Match_func_header, so that it returns the matched header without the enclosing white space. Match_func_header must still return None if there is no match. Here are some examples of matched and unmatched lines: Matched lines Unmatched lines def f(a): def f(): def f (a) : def if (a): def f12_(a5b): def f12_(a5b) def f(a=12): def f(a=3.14): def f(a=-12): def f(a=12-): def f(a='hello world'): def f('hello world'): def f(a="test"): def f(a="test): def f(a=fileName) : def f(a=2 fileName)