Python | os.path.expandvars() method

OS module in Python provides functions for interacting with the operating system. OS comes under Python’s standard utility modules. This module provides a portable way of using operating system dependent functionality. os.path the module is a submodule of OS module in Python used for common pathname manipulation.

os.path.expandvars() method in Python is used to expand the environment variables in the given path. It replaces substrings of the form $name or ${name} in the given path with the value of environment variable name.

If the given path contains malformed environment variable names or environment variables that do not exist then os.path.expandvars() method will left it unchanged.

On Windows, %name% expansion is also supported in addition to $name and ${name}expansion.

Syntax: os.path.expandvars(path)

Parameter:
path: A path-like object representing a file system path. A path-like object is either a string or bytes object representing a path.

Return Type: This method returns a string which represents the parameter with environment variables expanded.

Code #1: Use of os.path.expandvars() method

# Python program to explain os.path.expandvars() method

# importing os.path module
import os.path

# Path
path = "$HOME/file.txt"

# Expand the environment variables
# with their corresponding
# value in the given path
exp_var = os.path.expandvars(path)


# Print the given path with
# environment variables expanded
print(exp_var)


# Change the value of
# Environment variable 'HOME'

os.environ["HOME"] = "/home/GeeksForGeeks"

# Path
path = "$HOME/Documents/file.txt"

# Expand the environment variables
# with their corresponding
# value in the given path
exp_var = os.path.expandvars(path)

# Print the given path with
# environment variables expanded
print(exp_var)


# Create an environment variable
os.environ["USER"] = "ihritik"

# Path
path = "/home/${USER}/file.txt"

# Expand the environment variables
# with their corresponding
# value in the given path
exp_var = os.path.expandvars(path)

# Print the given path with
# environment variables expanded
print(exp_var)


# In the above example,
# os.path.expandvars() method replaced
# the environment variable 'HOME' and 'USER'
# with their corresponding values

Output:

/home/ihritik/file.txt
/home/GeeksForGeeks/Documents/file.txt
/home/ihritik/file.txt

Code #2: Use of os.path.expandvars() method (On Windows)

# Python program to explain os.path.expandvars() method

# importing os.path module
import os.path

# On Windows % name % expansions
# are supported in addition to
# $name and ${name}

# Path 1
path1 = R"% HOMEPATH %\Directory\file.txt"

# Path 2
path2 = R"C:\Users\$USERNAME\Directory\file.txt"

# Path 3
path3 = R"${TEMP}\file.txt"

# Expand the environment variables
# with their corresponding
# value in the given paths
exp_var1 = os.path.expandvars(path1)
exp_var2 = os.path.expandvars(path2)
exp_var3 = os.path.expandvars(path3)

# Print the given paths with
# environment variables expanded
print(exp_var1)
print(exp_var2)
print(exp_var3)


# In the above example
# os.path.expandvars() method
# replaced the environment variables
# 'HOMEPATH', 'USERNAME' and 'TEMP'
# with their corresponding values

Output:

\\Users\\Hritik\\\Directory\\file.txt
C:\\Users\\Hritik\\\Directory\\file.txt
C:\\Users\\Hritik\\AppData\\Local\\Temp\\file.txt

Code #3: If environment variable does not exists

# Python program to explain os.path.expandvars() method

# importing os.path module
import os.path

# If the environment variable
# is malformed or does not exist
# then the given path will be
# left unchanged

# Path
path = R"${MYHOME}/Directory/file.txt"

# Expand the environment variables
# with their corresponding
# value in the given paths
exp_var = os.path.expandvars(path)

# Print the given path with
# environment variables expanded
print(exp_var)


# As 'MYHOME' environment variable
# does not exists so
# os.path.expandvars() method
# will return the given path
# unchanged

Output:

${MYHOME}/Directory/file.txt

Reference: https://docs.python.org/3/library/os.path.html