recursive traversal of file

Re: recursive traversal of file

Xavier Decoret wrote:[color=blue]
> I am reading the lines of a file, executing appropriate command if a
> pattern is found. One of the pattern can be a input command whose effect
> should be to #include the file (possibly recursively)
>
> The main loop looks like this:
>
> data=[]
>
> try:
> file = open(fileName)
> line = file.readline()
> while line:
> if matchInputPatte rn(line,inputFi le):
> # help me here to parse inputFile
> elif matchDataPatter n(line):
> data.append(1)
> line = file.readline()
> except IOError, e:
> print 'I couldn\'t open file name',fileName
> sys.exit(1)
>
> Can you tell me if there is a simple way to do the part that says #help
> me!. Should I do a recursive function?[/color]

You could wrap all this in a function, let's call it import_file or whatever.
Then, upon encountering the #include pattern, you could do,

if matchInputPatte rn(line, inputFile):
import_file(som e_filename_extr acted_from_patt ern)

This *should* work, although I didn't test it. Also, it assumes that recursive
function calls share the same list ('data'). It would be cleaner to have
import_file create, fill and return its own list. In pseudocode:

def import_file(fil ename):
data = []
...
for line in lines:
if (pattern matches):
z = import_file(fil ename_from_patt ern)
data.extend(z)
...

return data

HTH,

--
Hans (hans@zephyrfal con.org)

Re: recursive traversal of file

To prevent a recursive infinite loop, keep a list of the current chain of
filenames being imported. Before importing filename_from_p attern, make sure
it is not in the list (else you will eventually loop through the same files
until your stack blows up or similar dire consequence). If the file is in
the list, you can skip it, or raise an exception.

-- Paul McGuire
Austin, TX
[color=blue]
>
> This *should* work, although I didn't test it. Also, it assumes that[/color]
recursive[color=blue]
> function calls share the same list ('data'). It would be cleaner to have
> import_file create, fill and return its own list. In pseudocode:
>
> def import_file(fil ename):
> data = []
> ...
> for line in lines:
> if (pattern matches):
> z = import_file(fil ename_from_patt ern)
> data.extend(z)
> ...
>
> return data
>
>[/color]