Searching a string in a multiple-file directory

[peruron]

Hello again!

I've been discussing the advantages of Python over C-Shell. I was asked if I can replace the use of "grep" in searching for a specific string in a multi-file directory - I have to go through all the files, and find all the occurrences of a specific string.
Can anyone suggest an idea?

Thanks!

[bartonc]

Hello again!

I've been discussing the advantages of Python over C-Shell. I was asked if I can replace the use of "grep" in searching for a specific string in a multi-file directory - I have to go through all the files, and find all the occurrences of a specific string.
Can anyone suggest an idea?

Thanks!

(IMO) Python can be used as a great adjunct to your OS's tools by writing very powerful scripts. But if the OS already has a tool that will do the job, then the only reason to write such a function would be for academic purposes. In that light, Python does have:

• The glob module (actually only one function: glob())
• Use glob() to get a list of files from a pattern according to the rules used by the Unix shell
• The re module
• Do Regular Expression matching on the entire contents fo the file

And there you'd have grep. Good practice, maybe on *nix, but very handy on an OS that doesn't have a native grep().

[peruron]

Okay, thanks, but I think we have a little misunderstanding: I'm interested in searching for a certain string inside the files, and not as a path name. If I understood correctly the glob module, it searches a given path.
My purpose is a bit more than academic - I'm trying to convert people to Python (:

[bartonc]

Okay, thanks, but I think we have a little misunderstanding: I'm interested in searching for a certain string inside the files, and not as a path name. If I understood correctly the glob module, it searches a given path.
My purpose is a bit more than academic - I'm trying to convert people to Python (:

Any misunderstanding is my fault. I have very little experience with unix style commands (maybe I'm thinking of something called egrep that searches a set of files (glob-style) and then applies a regex to each file).

Anyway, this type of script takes very few lines of python code and I find the docs (on Windows, anyway) to be very friendly.
The trickiest part is working with the re module which employs a pythonic interface (far from Perl-style syntax) and has a few odd flags for working with multi-line text (re.DOTALL, for example). You'll tend to find the usage:

import re
myPattObj = re.compile('some[regex]pattern')
resList = myPattObj.findall(someTextObject)

which in turn yields a bunch of match objects (assuming a match) that have their own set of attributes. It's all so very OOP - perhaps the bigger conversion issue..?

[EDIT: maybe we could just write a people-to-python converter-LOL]

[ghostdog74]

interested in searching for a certain string inside the files, and not as a path name.

you can use os.walk, or os.listdir() to get a list of files. then iterate over them using for loop...while iterating over each file, open the file for reading and using a for loop to iterate the files line by line. You can check for string patterns using the "in" operator..eg if "string_to_search" in line: .....for more complex string matching, you can use regular expressions (as mentioned by barton). that's what happens to grep at the back end too...regular expressions..however do note that not every problem needs to be solved by regular expression.

If I understood correctly the glob module, it searches a given path.

yes it does.

My purpose is a bit more than academic - I'm trying to convert people to Python (:

wise move.

[bartonc]

Okay, thanks, but I think we have a little misunderstanding: I'm interested in searching for a certain string inside the files, and not as a path name. If I understood correctly the glob module, it searches a given path.
My purpose is a bit more than academic - I'm trying to convert people to Python (:

Here's a great link for you: Python Advocacy HOWTO.