RegEx:

A RegEx, or Regular Expression, is a sequence of characters that forms a search pattern.

RegEx can be used to check if a string contains the specified search pattern.

RegEx Module Python has a built-in package called re, which can be used to work with Regular Expressions.

Import the re module:

import re

RegEx in Python When you have imported the re module, you can start using regular expressions:

Example
Search the string to see if it starts with "The" and ends with "Spain":

import re

txt = "The rain in Spain"
x = re.search("^The.*Spain$", txt)

RegEx Functions The re module offers a set of functions that allows us to search a string for a match:

Function Description findall Returns a list containing all matches search Returns a Match object if there is a match anywhere in the string split Returns a list where the string has been split at each match sub Replaces one or many matches with a string

Function	Description
findall	Returns a list containing all matches
search	Returns a Match object if there is a match anywhere in the string
split	Returns a list where the string has been split at each match
sub	Replaces one or many matches with a string

High-level file operations in Python (shutil):

A number of functions for hgh level operations on files and directories have been defined in shutil module of Python’s standard library.

copy() This function copies a file to a specified file in same or other directory. First parameter to the function is a string representation of existing file. Second argument is either name of resultant file or directory. If it is a directory, the file is coped in it with same name. The metadata of original file is not maintained.

>>> import shutil
>>> shutil.copy("hello.py","newdir/")
'newdir/hello.py'

copy2() This function is similar to copy() function except for the fact that it retains metadata of source file. For example the date modified property of resulting file will be similar to original file.

>>> shutil.copy2('person.py', 'newdir/')
'newdir/person.py'

copyfile() Two string arguments of this function represent file names.It means the original file is copied by the specified name in the same directory.

>>> shutil.copyfile('start.py', 'end.py')
'end.py'

copyfileobj()

The parameters of this function are file objects rather than strings representing files. The file objects are obtained by open() function. Original file should have read permission and resulting file hould be opened with write permission.

>>> f1=open('hello.py','r')
>>> f2=open('python.py','w')
>>> shutil.copyfileobj('f1', 'f2')
>>> shutil.copyfileobj(f1, f2)

move() This function recursively moves file and directories from on directory to other.

>>> shutil.move('hello.py', 'newdir/')
'newdir/hello.py'

copytree() This function recursively copies file and subdirectories in one directory to another directory. Names of two parameters must be string. Directory of second parameter’s name should not exist earlier. To copy individual files copy2() function is internally used.

>>> shutil.copytree('dir1','dir2')
'dir2'

rmtree() This function removes files and subdirectories in the specified directory.

>>> shutil.rmtree('dir2')
>>> shutil.move('hello.py', 'newdir/')
'newdir/hello.py'

disk_usage() This function retrieves usage statistics of directory given.

>>> shutil.disk_usage('c:\\python36\\dir1')
usage(total=245681352704, used=84932993024, free=160748359680)

which() This function returns path to an executable.

>>> shutil.which('calc')
'C:\\WINDOWS\\system32\\calc.EXE'

make_archive() This function builds an archive (zip or tar) of files in the root directory.

>>> root_dir='newdir'
>>> shutil.make_archive("newdirarch","zip",root_dir)
'C:\\python36\\newdirarch.zip'

get_archive_formats() This function gives of all supported archive formats.

>>> shutil.get_archive_formats()
[('bztar', "bzip2'ed tar-file"), ('gztar', "gzip'ed tar-file"), ('tar', 'uncompressed tar file'), ('xztar', "xz'ed tar-file"), ('zip', 'ZIP file')]

unpack_archive() This functions extracts files in the given archive. Second parameter is the directory in which file are to be extracted. If not given, the unpacking is performed in current directory.

>>> shutil.unpack_archive('newdirarch.zip','newdir')