glob – Filename pattern matching

Glob module searches all path names looking for files matching a specified pattern according to the rules dictated by the Unix shell. Results so obtained are returned in arbitrary order. Some requirements need traversal through a list of files at some location, mostly having a specific pattern. Python’s glob module has several functions that can help in listing files that match a given pattern under a specified folder.  

Pattern matching is done using os.scandir() and fnmatch.fnmatch() functions, and not by actually invoking a sub-shell. Unlike fnmatch.fnmatch(), glob treats filenames beginning with a dot (.) as special cases. For tilde and shell variable expansion, os.path.expanduser() and os.path.expandvars() functions are used.

Pattern rules 

• Follow standard Unix path expansion rules.
• Special characters supported : two different wild-cards-  *, ?  and character ranges expressed in [].
• The pattern rules are applied to segments of the filename (stopping at the path separator, /).
• Paths in the pattern can be relative or absolute.

Application

• It is useful in any situation where your program needs to look for a list of files on the file system with names matching a pattern.
• If you need a list of filenames that have a certain extension, prefix, or any common string in the middle, use glob instead of writing code to scan the directory contents yourself.

Functions in Glob:

• glob(pathname, *, recursive=False)- It returns list of path names that match pathname given, which must be a string containing a path specification. List can be empty too.
• iglob(pathname, *, recursive=False)- This method creates a Python generator object which is used to list files under a given directory. Also returns an iterator that yields the same values as glob() without actually storing them all simultaneously.
• escape(pathname)- It allows escaping the given character sequence. You can find it handy for locating files with certain characters in their file names and matching an arbitrary literal string that may have special characters in it.

Given below is the implementation to help you understand how this module can be put to practice:

Example 1:

Python3

import glob

# search .py files
# in the current working directory
for py in glob.glob("*.py"):
    print(py)

Output :

Example 2: Program to depict wildcard characters and ranges

If recursive is true, the pattern “**” will match any files and zero or more directories, subdirectories and symbolic links to directories. Using the “**” pattern in large directory trees may consume an inordinate amount of time. 

Python3

import glob

# Using character ranges []
print('Finding file using character ranges [] :- ')
print(glob.glob('./[0-9].*'))

# Using wildcard character *
print('\n Finding file using wildcard character * :- ')
print(glob.glob('*.gif'))

# Using wildcard character ?
print('\n Finding file using wildcard character ? :- ')
print(glob.glob('?.gif'))

# Using recursive attribute
print('\n Finding files using recursive attribute :- ')
print(glob.glob('**/*.txt', recursive=True))

Output :

Example 3:

Python3

import glob

gen = glob.iglob("*.py")
# returns class type of gen
type(gen)

for py in gen:
    print(py)

Output :

Example 4:

Python3

import glob

char_seq = "-_#"

for spcl_char in char_seq:
    esc_set = "*" + glob.escape(spcl_char) + "*" + ".py"

    for py in (glob.glob(esc_set)):
        print(py)

Output :