music21.common.fileTools

Tools for working with files

Functions

music21.common.fileTools.cd(targetDir)

Useful for a temporary cd for use in a with statement:

with cd(‘/Library/’):

os.system(make)

will switch temporarily, and then switch back when leaving.

music21.common.fileTools.preparePathClassesForUnpickling()

When we need to unpickle a function that might have relative paths (like some music21 stream options), Windows chokes if the PosixPath is not defined, but usually can still unpickle easily.

music21.common.fileTools.readFileEncodingSafe(filePath, firstGuess='utf-8') → str

Slow, but will read a file of unknown encoding as safely as possible using the chardet package. Mostly obsolete in the utf-8 world of today, but useful for older code

Let’s try to load the music21.common.__init__.py file as ascii – it has a copyright symbol near the top, so it won’t load in Python3:

>>> import os
>>> c = str(common.getSourceFilePath() / 'common' / '__init__.py')
>>> f = open(c, encoding='ascii')
>>> data = f.read()
Traceback (most recent call last):
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position ...:
    ordinal not in range(128)

That won’t do! Now I know that it is in utf-8, but maybe you don’t. Or it could be an old Humdrum or Noteworthy file with Windows or unknown encoding. This will load it as safely as possible.

>>> data = common.readFileEncodingSafe(c)
>>> data[83:106]
'Name:         common.py'

Well, that’s nothing, since the first guess here is utf-8, and it’s right. So let’s give a worse first guess:

>>> data = common.readFileEncodingSafe(c, firstGuess='SHIFT_JIS')  # old Japanese standard
>>> data[83:106]
'Name:         common.py'

It worked!

Note that trying lots of encodings is slow enough when the first guess is wrong that the firstGuess should be set to something reasonable like ‘utf-8’ or ‘ascii’.

music21.common.fileTools.readPickleGzip(filePath: str | Path) → Any

Read a gzip-compressed pickle file, uncompress it, unpickle it, and return the contents.

music21.common.fileTools.restorePathClassesAfterUnpickling()

After unpickling, leave pathlib alone.

music21.common.fileTools.runSubprocessCapturingStderr(subprocessCommand)

Run a subprocess command, capturing stderr and only show the error if an exception is raised.