Topic: Python problems

[sand_man]

I've been playing around with python today and I'm having problems with file IO.
Since my C file parser in C was a slight failure, I decided to try and use Python to do the same thing (because I heard that Python, Perl and other scripting languages are good for string parsing etc).
The problem is I don't know how to test a file object for EOF.

Code: [Select]


in_file = open("main.c","r")
out_file = open("out.txt","w")
out_file.write("")

#while ??:  <---WHAT DO I TEST FOR???
c = 0
is_comment = 0
line = in_file.readline()

while c < len(line):
    if line[c] == "/" and line[c+1] == "/" and is_comment == 0:
        out_file.write("")
        out_file.write(line[c])
        is_comment = 1
    else:
        out_file.write(line[c])
    c = c + 1
   
if is_comment:
    out_file.write("")


out_file.write("\n")
out_file.close()
in_file.close()

I've checked the docs and several tutorials and it just makes no sense to me.

(the color labels and code labels have been edited because it makes the post look funny)

[sand_man]

It seems I may have found a solution before you all could even reply

does this seem right?

Code: [Select]


in_file = open("main.c","r")
out_file = open("out.txt","w")
out_file.write("\n")

line = in_file.readline()
while (line):
    c = 0
    is_comment = 0


    while c < len(line):
        if line[c] == "/" and line[c+1] == "/" and is_comment == 0:
            out_file.write("")
            out_file.write(line[c])
            is_comment = 1
        else:
            out_file.write(line[c])
        c = c + 1
   
    if is_comment:
        out_file.write("")

    line = in_file.readline()


out_file.write("\n")
out_file.close()
in_file.close()

[ygfperson]

I haven't used python in a while but wouldn't it make more sense to test in_file instead?

[sand_man]

That is what I thought but it just kept looping. I probably wasn't doing it properly.
Anyway, if eof is reached then loop will be 0 so this works.

[sand_man]

This is my work so far. As messy as it looks, it works nicely. But I can't work out how to identify the keywords. I assume I should use regex? I need some help with this.

Code: [Select]



in_file = open("capp.cpp","r")
out_file = open("out.txt","w")
out_file.write("\n")

keywords = ["auto","double","int","long",\
            "break","else","switch","char"\
            "case","enum","register","typedef",\
            "extern","return","union","const",\
            "float","short","unsigned","continue",\
            "for","signed","void","default","goto",\
            "sizeof","volatile","do","if","static","while"]

alpha = ['a','b','c','d','e','f','g','h',\
         'i','j','k','l','m','n','o','p',\
         'q','r','s','t','u','v','w','x','y','z']


line = in_file.readline()
is_mcomment = 0
is_string  = 0
is_comment = 0
while (line):
    c = 0
   
    is_scomment = 0
    is_prepro  = 0
    is_number = 0

   
    while c < len(line):
       

        ### MULTI LINE COMMENTS ###
        if line[c] == "/" and line[c+1] == "*":
            if is_prepro:
                out_file.write("")
                is_prepro = 0
            out_file.write("")
            is_mcomment = 1
            is_comment = 1
        elif line[c] == "/" and line[c+1] == "/":
            if is_prepro:
                out_file.write("")
                is_prepro = 0
            out_file.write("")
            is_scomment = 1
            is_comment = 1

        if line[c] == "#" and not is_comment:
            out_file.write("")
            is_prepro = 1

       
        if line[c] == "\"" and not is_comment:
            if not is_string:
                out_file.write("")
                is_string = 1
            else:
                is_string = 2
                   
        if line[c].isdigit() and not is_prepro and not is_string and not is_comment:
            if not line[c-1] in alpha and not line[c+1] in alpha:
                out_file.write("")
                is_number = 1
       
       
           
        out_file.write(line[c])

        ### ENDING STRINGS, DIGITS AND MULTI LINE COMMENTS ###
        if line[c] == "*" and line[c+1] == "/":
            c = c + 1 # No idea why this needs to be done
            out_file.write("")
            is_mcomment = 0
            if is_mcomment == 0 and is_scomment == 0:
                is_comment == 0
        if is_string == 2:
            out_file.write("")
            is_string = 0
        if is_number == 1:
            out_file.write("")
            is_number = 0

       
       
        c = c + 1

       
    ### ENDING SINGLE LINE COMMENTS AND PREPROCESSOR ###
    if is_scomment:
        out_file.write("")
        is_scomment = 0
        if is_mcomment == 0 and is_scomment == 0:
                is_comment == 0
    if is_prepro:
        out_file.write("")
        is_prepro = 0
   
    line = in_file.readline()


out_file.write("\n")
out_file.close()
in_file.close()


[webwhy]

you can test for membership in a python sequence object such as your "keywords" list with the in operator

Code: [Select]


keywords = ['int', 'double', 'long', 'static']
if 'int' in keywords:
    print 'found'


Also you can you the read the contents of the file into a sequence object with the readlines or xreadlines method on the file object.

Code: [Select]


f = open('main.cpp', 'r')
for line in f.xreadlines():
    print line
f.close()