Python Programming for Biology: Bioinformatics and Beyond

Method (os.)

Description

chdir(path)

Changes the current working directory; for specifying

relative file-system paths.

getenv(varname,

default)

Gets an environment variable of a given name, with optional

default value if it doesn’t exist.

putenv(varname,

value)

Sets an environment variable of a given name, with a given

value.

uname()

In Python 2 gives a tuple containing five items detailing the

current operating-system type. In Python 3 gives a

uname_result object, representing the same kind of

information.

unsetenv(varname)

Deletes a named environment variable.

tmpfile()

Creates an unnamed, temporary file object with mode ‘w+b’

(write binary) which only exists for the current session.

access(path, mode)

Gets status information for a file-system path, using a

specified mode to check if the path exists, is readable,

writeable or executable.

chdir(path)

Changes the current working directory (for relative paths) to

the specified path.

getcwd()

Retrieves a path string representing the current working

directory; for relative paths.

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chmod(path,

mode)

Changes read, write and execution permissions for a given

path. Equivalent to UNIX ‘chmod’.

chown(path, uid,

gid)

Changes the user and group ownership or a given path.

Equivalent to UNIX ‘chown’. Note this can be used on

Windows systems but only sets the read-only status.

link(target,

linkName)

Creates a (hard) file link connecting a stated source/target

path with a specified name.

listdir(path)

Creates a list of file and directory names for a specified file-

system path.

mkdir(path, mode)

Creates a new, empty directory with a specified file-system

path. Optional argument to specify the file access mode.

makedirs(path,

mode)

Recursively creates a new, empty directory with a stated

path, including any intervening directories if they do not

exist. Optional argument to specify the file access mode.

remove(path)

Deletes a file of specified path. Gives an OSError if the path

is a directory (use rmdir() for deleting directories).

removedirs(path)

Recursively removes a directory, if empty, and then parent

directories that are empty. Gives an OSError if the directory

is not empty.

rename(old, new)

Change the name of a file or directory.

rmdir(path)

Removes a specified directory path from a file system, if it

is empty, otherwise it gives an OSError.

stat(path)

Generates a status object that has attributes detailing

information about a given path, including access

permissions, device, owner, group, file size, access time,

modification time etc.

symlink(target,

linkName)

Creates a symbolic (soft) link to a given path.

unlink(path)

Same as os.remove().

walk(top,

topDown, onError,

followLinks)

Creates a generator that yields (parentPath, dirNames,

fileNames) tuples that recursively walk through a directory

and any sub-directories.

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system(command)

Issues a command to the operating system as if it were from

a command line prompt. It is recommended to use

subprocess.call() instead.