Python| os.path.expandvars() 方法

Python中的OS 模块提供了与操作系统交互的功能。操作系统属于 Python 的标准实用程序模块。该模块提供了一种使用操作系统相关功能的可移植方式。 os.path模块是Python中OS 模块的子模块，用于常见的路径名操作。

Python中的os.path.expandvars()方法用于扩展给定路径中的环境变量。它将给定路径中形式为 $name或${name}的子字符串替换为环境变量name的值。

如果给定路径包含格式错误的环境变量名称或不存在的环境变量，则os.path.expandvars()方法将使其保持不变。

在Windows上，除了$name和${name}扩展之外，还支持%name%扩展。

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.

编程需要懂一点英语

代码 #1：使用 os.path.expandvars() 方法

# 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

输出：

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

代码 #2：使用 os.path.expandvars() 方法（在 Windows 上）

# 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

输出：

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

代码#3：如果环境变量不存在

# 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

输出：

${MYHOME}/Directory/file.txt

参考： https://docs。 Python.org/3/library/os.path.html