until you’ve learned what each name means (I’ve let this line-wrap and removed most
of this list to save space—run the command on your own):
>>> import os
>>> dir(os)
['F_OK', 'MutableMapping', 'O_APPEND', 'O_BINARY', 'O_CREAT', 'O_EXCL', 'O_NOINH
ERIT', 'O_RANDOM', 'O_RDONLY', 'O_RDWR', 'O_SEQUENTIAL', 'O_SHORT_LIVED', 'O_TEM
PORARY', 'O_TEXT', 'O_TRUNC', 'O_WRONLY', 'P_DETACH', 'P_NOWAIT', 'P_NOWAITO', '
P_OVERLAY', 'P_WAIT', 'R_OK', 'SEEK_CUR', 'SEEK_END', 'SEEK_SET', 'TMP_MAX',
...9 lines removed here...
'pardir', 'path', 'pathsep', 'pipe', 'popen', 'putenv', 'read', 'remove', 'rem
ovedirs', 'rename', 'renames', 'rmdir', 'sep', 'spawnl', 'spawnle', 'spawnv', 's
pawnve', 'startfile', 'stat', 'stat_float_times', 'stat_result', 'statvfs_result
', 'strerror', 'sys', 'system', 'times', 'umask', 'unlink', 'urandom', 'utime',
'waitpid', 'walk', 'write']Besides all of these, the nested os.path module exports even more tools, most of which
are related to processing file and directory names portably:
>>> dir(os.path)
['__all__', '__builtins__', '__doc__', '__file__', '__name__', '__package__',
'_get_altsep', '_get_bothseps', '_get_colon', '_get_dot', '_get_empty',
'_get_sep', '_getfullpathname', 'abspath', 'altsep', 'basename', 'commonprefix',
'curdir', 'defpath', 'devnull', 'dirname', 'exists', 'expanduser', 'expandvars',
'extsep', 'genericpath', 'getatime', 'getctime', 'getmtime', 'getsize', 'isabs',
'isdir', 'isfile', 'islink', 'ismount', 'join', 'lexists', 'normcase', 'normpath',
'os', 'pardir', 'pathsep', 'realpath', 'relpath', 'sep', 'split', 'splitdrive',
'splitext', 'splitunc', 'stat', 'supports_unicode_filenames', 'sys']Administrative Tools
Just in case those massive listings aren’t quite enough to go on, let’s experiment inter-
actively with some of the more commonly used os tools. Like sys, the os module comes
with a collection of informational and administrative tools:
>>> os.getpid()
7980
>>> os.getcwd()
'C:\\PP4thEd\\Examples\\PP4E\\System'>>> os.chdir(r'C:\Users')
>>> os.getcwd()
'C:\\Users'As shown here, the os.getpid function gives the calling process’s process ID (a unique
system-defined identifier for a running program, useful for process control and unique
name creation), and os.getcwd returns the current working directory. The current
working directory is where files opened by your script are assumed to live, unless their
names include explicit directory paths. That’s why earlier I told you to run the following
command in the directory where more.py lives:
C:\...\PP4E\System> python more.py more.pyIntroducing the os Module | 91