Func_headers.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 lf (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)