safer 0.9.10

Try to import all modules below a given root

✏️safer: a safer file writer ✏️

Safely write or print to a file in a context where the original file is only overwritten if the context completes without throwing an exception.

Tested on Python versions 2.7, and 3.4 through 3.8.

Install safer from the command line using pip:

pip3 install safer

NOTE: safer uses a temporary file which is copied over the original file after the context completes successfully, so it temporarily uses as much disk space as the old file and the new file put together.

EXAMPLES

safer.writer

# dangerous
with open(config_filename, 'w') as fp:
    json.dump(cfg, fp)    # If this fails, the config file is corrupted

# safer
with safer.writer(config_filename) as fp:
    json.dump(cfg, fp)    # If this fails, the config file is untouched

safer.printer

# dangerous
with open(configs_filename, 'w') as fp:
    for cfg in configs:
        print(json.dumps(cfg), file=fp)  # Corrupts the file on failure

# safer
with safer.printer(configs_filename) as print:
    for cfg in configs:
        print(json.dumps(cfg))          # Cannot corrupt the file

API call documentation

safer.writer(file, mode='w', create_parents=False, delete_failures=True, suffix='.tmp', **kwargs)

A context that yields the writable stream returned from open(), but undoes any changes to the file if there’s an exception.

Arguments:

file:

Path to the file to be opened

mode:

Mode string passed to open()

create_parents:

If True, all parent directories are automatically created

delete_failures:

Are partial files deleted if the context terminates with an exception?

suffix:

File suffix to use for temporary files

kwargs:

Keywords passed to built-in open

safer.printer(file, mode='w', create_parents=False, delete_failures=True, suffix='.tmp', **kwargs)

A context that yields a function that prints to the opened file, but undoes any changes to the file if there’s an exception.

Arguments:

file:

Path to the file to be opened

mode:

Mode string passed to open()

create_parents:

If True, all parent directories are automatically created

delete_failures:

Are partial files deleted if the context terminates with an exception?

suffix:

File suffix to use for temporary files

kwargs:

Keywords passed to built-in open