strif

Strif is a tiny (only a few hundred loc) library of string- and file-related utilities for Python 2.7 and 3.6.

The goal is to complement the standard libs, not replace or wrap them. It’s basically an assembly of some functions and tricks that have repeatedly shown value in various projects.

Why bother, if it’s so short? Because it saves time, fills in gaps, avoids clumsy repetition, and has zero dependencies.

Is it mature? I’ve used these tools individually in production situations, but it’s not a comprehensively tested library.

Highlights

Atomic file operations plus extras

It’s generally good practice when creating files to write to a file with a temporary name, and move it to a final location once the file is complete. This way, you never leave partial, incorrect versions of files in a directory due to interruptions or failures. For example, these can be used in place of shutil.copyfile or shutil.copytree:

copyfile_atomic(source_path, dest_path, make_parents=True, backup_suffix=None)
copytree_atomic(source_path, dest_path, make_parents=True, backup_suffix=None, symlinks=False)

You also have convenience options for creating parent directories of the target, if they don’t exist. And you can keep a backup of the target, rather than clobber it, if you prefer. Used judiciously, these options can save you some boilerplate coding.

Syntax sugar for atomic file creation

Similarly, you have syntax sugar for creating files or directories atomically using with:

with atomic_output_file("some-dir/my-final-output.txt",
                        make_parents=True, backup_suffix=".old.{timestamp}") as temp_target:
  with open(temp_target, "w") as f:
    f.write("some contents")

Now if there is some issue during write, the output will instead be at a temporary location in the same directory. (It will have a name like some-dir/my-final-output.txt.partial.XXXXX.) This ensures integrity of the file appearing in the final location.

Optionally, as a bonus, if you would have clobbered a previous output, it keeps a backup with a (fixed or uniquely timestamped) suffix.

Syntax sugar for temporary files

Syntax sugar for auto-deleting temporary files or directories using with:

with temp_output_file("my-scratch.") as (fd, path):
  # Do a bunch of stuff with the opened file descriptor or path, knowing
  # it will be removed assuming successful termination.


with temp_output_dir("work-dir.", dir="/var/tmp") as work_dir:
  # Create some files in the now-existing path work_dir, and it will be
  # deleted afterwords.

Note these don’t delete files in case of error, which is usually what you want. Add always_clean=True if you want the temporary file or directory to be removed no matter what.

Miscellany

• Secure random base 36 identifiers: Digression: Use base 36 in general for random id strings. It is briefer than hex, avoids ugly non-alphanumeric characters like base 64, and is case insensitive, which is generally wise (e.g. due to MacOS case-insensitive filesystems).
• Secure random timestamped identifiers. These are similar, but start with an ISO timestamp plus a base 36 identifier, so that they sort chronologically but are still unique.
• Abbreviations for strings and lists: Abbreviate strings and lists in a pretty way, truncating items and adding ellipses.

Installation

pip install strif

Or add as a dependency in your setup.py.

Further Information

pydoc strif

Contributing

Please file issues or PRs!

License

Apache 2.