aka 1.0.3

Rename/copy files using Python code

Abstract

This package provides a command line utility called aka for swiftly renaming (or copying) files using Python code. This makes it easy to rename files even when the changes you are making are quite complicated. It always renames files in two passes to avoid collisions; it tries to detect miscellaneous errors in advance; and if errors occur underways it will put you in an emergency mode to resolve the problem or roll back changes. It also provides the functions aka.rename and aka.copy, which is the underlying interface.

The problem being solved

Lets say you have a directory with the files File0, File1, and File2. Then some people comes along and complains (rightly or wrongly) that the numbering starts at zero. So you decide to write a program to rename all those files, but a problem arises. You cannot do it in any order you like, you have to start with File2 -> File3 in order to avoid conflicts. It’d be nice to just write a function that knows how to change the names of individual files and let another program sort out the rest. This is what aka.rename is about:

>>> import aka
>>> from contex import rules
>>> def machine(fn):
        return rules(r'File(\d+)', {1: lambda digit: int(digit) + 1}).apply(fn)
>>> machine('File42')
'File43'
>>> aka.rename(machine)
Actions to be taken (simplified; doesn't show the temporary stage):
  /home/uglemat/Documents/File0           -> /home/uglemat/Documents/File1
  /home/uglemat/Documents/File1           -> /home/uglemat/Documents/File2
  /home/uglemat/Documents/File2           -> /home/uglemat/Documents/File3
Target directories:
  /home/uglemat/Documents

The files will be renamed as shown above (in two passes though, in order to avoid
collisions). This program searched for name conflicts in all target directories
and did not find any. If errors do pop up, you'll be taken to an emergency mode
where you can roll back changes. Continue? [N/y]: y
Renaming /home/uglemat/Documents/File0 -> /tmp/aka_maok91r8/File0
Renaming /home/uglemat/Documents/File1 -> /tmp/aka_maok91r8/File1
Renaming /home/uglemat/Documents/File2 -> /tmp/aka_maok91r8/File2
Renaming /tmp/aka_maok91r8/File0 -> /home/uglemat/Documents/File1
Renaming /tmp/aka_maok91r8/File1 -> /home/uglemat/Documents/File2
Renaming /tmp/aka_maok91r8/File2 -> /home/uglemat/Documents/File3
True

I used contex.rules to manipulate the string, but you can do whatever you like inside machine, you just need to return the new name of the file.

By default it renames files in the current working directory, but that can be changed with the location argument to aka.rename. aka.copy is basically the same, it just copies files instead. Read the docstrings of those functions to learn the details.

Command line utility

That’s all fine and dandy, but when you just have some files and you need to rename them, you want to do it with a command line utility. This is the basics:

$ aka --help
Useful information ...
$ aka -p 'fn+".jpg"'

That will add a “.jpg” suffix to all files in the working directory. But lets do what we did above with aka.rename:

$ aka -p 'rules(r"File(\d+)", {1: lambda digit: int(digit) + 1})'

The expression after -p doesn’t need to be a new filename, it can also be a unary callable (like machine above) that returns the new filename. That is why the example above works; contex.rules returns a callable. If you want to copy instead of rename, just add in the -c option:

$ aka -c -p 'rules(r"File(\d+)", {1: lambda digit: int(digit) + 1})'

 -- COPYING FILES IN . --

ERROR: /home/uglemat/Documents/File1 -> /home/uglemat/Documents/File2 is a conflict!
ERROR: /home/uglemat/Documents/File2 -> /home/uglemat/Documents/File3 is a conflict!
Aborting...

Err, yes, that won’t work, of course. Good thing aka detects naming conflicts in advance!

More complicated renaming schemes

That’s great, but what if it’s not a simple one-liner? Then you need to create a new file, write some python code, launch the python interpreter, import the stuff you need… It’s cumbersome, which is why aka can help with that:

$ aka -e emacs

This will launch emacs and take you to a temporary file which looks kind of like this:

import re
from os.path import join
from contex import rules

# Directories in which to perform changes:
#   /home/uglemat/Documents

def rename(fn, dirname):
    return fn

Your job is to complete rename, and when you exit the editor it will do the job (after asking you if you want to continue).

Lets do something more advanced, say you have lots of files in ~/Documents/files of the format File<num> and you want to split them into the folders odd and even, like this:

~/Documents/files $ for i in {0..20}; do touch "File$i"; done
~/Documents/files $ ls
File0  File1  File10  File11  File12  File13  File14  File15  File16  File17  File18  File19  File2  File20  File3  File4  File5  File6  File7  File8  File9
~/Documents/files $ mkdir odd even

There is a slight problem in that you can’t rename odd and even, but they are in the same directory. You just got to make sure that the rename function returns a falsy value for those filenames (btw, aka treats directories like files and will rename them too). Lets go to the editor with aka -e 'emacs -nw' and write this:

import re
from os.path import join
from contex import rules

# Directories in which to perform changes:
#   /home/uglemat/Documents/files

def rename(fn, dirname):
    match = re.search(r'\d+', fn)
    if match:
        digit = int(match.group(0))
        return join('even' if even(digit) else 'odd', fn)


def even(d):
    return (d % 2) == 0

The directories odd and even doesn’t match, so rename returns None for those names and thus they are ignored, and the code above works as expected:

~/Documents/files $ aka -e 'emacs -nw'
running $ emacs -nw +9:14 /tmp/aka_3uvuyn8c.py
Aka: Proceed? [Y/n]: y

 -- RENAMING FILES IN . --

Actions to be taken (simplified; doesn't show the temporary stage):
  /home/uglemat/Documents/files/File3           -> /home/uglemat/Documents/files/odd/File3
  /home/uglemat/Documents/files/File18          -> /home/uglemat/Documents/files/even/File18
  /home/uglemat/Documents/files/File13          -> /home/uglemat/Documents/files/odd/File13
  ...
Target directories:
  /home/uglemat/Documents/files/odd
  /home/uglemat/Documents/files/even

The files will be renamed as shown above (in two passes though, in order to avoid
collisions). This program searched for name conflicts in all target directories
and did not find any. If errors do pop up, you'll be taken to an emergency mode
where you can roll back changes. Continue? [N/y]: y
Renaming /home/uglemat/Documents/files/File3 -> /tmp/aka_st72r5jp/File3
Renaming /home/uglemat/Documents/files/File18 -> /tmp/aka_st72r5jp/File18
Renaming /home/uglemat/Documents/files/File13 -> /tmp/aka_st72r5jp/File13
...
Renaming /tmp/aka_st72r5jp/File3 -> /home/uglemat/Documents/files/odd/File3
Renaming /tmp/aka_st72r5jp/File18 -> /home/uglemat/Documents/files/even/File18
Renaming /tmp/aka_st72r5jp/File13 -> /home/uglemat/Documents/files/odd/File13
~/Documents/files $ ls *
even:
File0  File10  File12  File14  File16  File18  File2  File20  File4  File6  File8

odd:
File1  File11  File13  File15  File17  File19  File3  File5  File7  File9

Rollbacks

To test the rollback feature of aka, lets first launch this command:

$ aka -p 'rules(r"File(\d+)", {1: lambda digit: int(digit) + 1})'

 -- RENAMING FILES IN . --

Actions to be taken (simplified; doesn't show the temporary stage):
  /home/uglemat/Documents/File3           -> /home/uglemat/Documents/File4
  /home/uglemat/Documents/File1           -> /home/uglemat/Documents/File2
  /home/uglemat/Documents/File2           -> /home/uglemat/Documents/File3
Target directories:
  /home/uglemat/Documents

The files will be renamed as shown above (in two passes though, in order to avoid
collisions). This program searched for name conflicts in all target directories
and did not find any. If errors do pop up, you'll be taken to an emergency mode
where you can roll back changes. Continue? [N/y]:

Now it’s waiting for confirmation from the user. So we have time to do some sabotage in another shell:

$ touch File4
$ ls
File1  File2  File3  File4

In the first shell, lets enter y to see how it fails:

Renaming /home/uglemat/Documents/File3 -> /tmp/aka_1ozr4w4b/File3
Renaming /home/uglemat/Documents/File1 -> /tmp/aka_1ozr4w4b/File1
Renaming /home/uglemat/Documents/File2 -> /tmp/aka_1ozr4w4b/File2
Renaming /tmp/aka_1ozr4w4b/File3 -> /home/uglemat/Documents/File4


EMERGENCY MODE: File /home/uglemat/Documents/File4 already exists!
ERROR: Error happened when trying to rename /tmp/aka_1ozr4w4b/File3 -> /home/uglemat/Documents/File4

What should the program do?
retry    : try again (presumably you've fixed something in the meantime)
rollback : attempt to undo changes (except for the ones previously continue'd)
showroll : show which actions will be taken if you choose `rollback`
exit     : exit the program
continue : ignore the error and move on
>

Oh my, looks like things didn’t go as planned. You’re now in the emergency prompt of aka. You can easily fix the problem by deleting File4 and entering retry, but that’s boring. Let’s first see what happens when you select continue:

> continue
Renaming /tmp/aka_1ozr4w4b/File1 -> /home/uglemat/Documents/File2
Renaming /tmp/aka_1ozr4w4b/File2 -> /home/uglemat/Documents/File3
LOST FILES IN TEMP DIR: '/tmp/aka_1ozr4w4b'
$ ls /tmp/aka_1ozr4w4b
File3

It’s not very nice that it just left the file in the temp dir. continue is probably rarely a good option. Lets be more sophisticated and choose rollback:

> showroll
Rollback actions:
  /tmp/aka_1ozr4w4b/File2              -> /home/uglemat/Documents/File2
  /tmp/aka_1ozr4w4b/File1              -> /home/uglemat/Documents/File1
  /tmp/aka_1ozr4w4b/File3              -> /home/uglemat/Documents/File3
What should the program do?
retry    : try again (presumably you've fixed something in the meantime)
rollback : attempt to undo changes (except for the ones previously continue'd)
showroll : show which actions will be taken if you choose `rollback`
exit     : exit the program
continue : ignore the error and move on
> rollback
Rollback renaming /tmp/aka_1ozr4w4b/File2 -> /home/uglemat/Documents/File2
Rollback renaming /tmp/aka_1ozr4w4b/File1 -> /home/uglemat/Documents/File1
Rollback renaming /tmp/aka_1ozr4w4b/File3 -> /home/uglemat/Documents/File3
$ ls
File1  File2  File3  File4

Rollback will “undo” all previous actions, in the reverse order that they were “done’d”. If you use the --copy option then the undoing consists of deleting files already copied. If any of the rollback actions fails, then aka will ignore it and try to undo as much as possible.

Installing

aka works only in Python 3.

Install with $ pip3 install aka. You might want to replace pip3 with pip, depending on how your system is configured.

Windows Compatability

I developed this program on GNU/Linux, but it should be working on Windows as well. It understands that filenames are case insensitive on Windows when checking for naming conflicts, yet the case sensitivity is preserved when the actual renames are done.

Developing

Aka has some tests. Run $ nosetests or $ python3 setup.py test to run the tests. The code is hosted at https://notabug.org/Uglemat/aka

You can install in development mode with $ python3 setup.py develop, then your changes to aka will take effect immediately. Launch the same command with the --uninstall option to (kind of) remove.

License

The code is licensed under the GNU General Public License 3 or later. This README file is public domain.