zoukankan      html  css  js  c++  java
  • [Python] Pitfalls: Be Careful with os.chdir

    One thing you need to keep in mind is that when using os.chdir to change the working directory of current programme (script), make sure if we need to come back to the current working directory again.

    Using os.chdir to change the current working directory anywhere in the programme will effect permanently, regardless if you are using it in a function or not, see the following example:

     1 import os
     2 
     3 def chdir_in_func():
     4     print "Before chaning, in func"
     5     print os.getcwd()
     6     os.chdir("/home/")
     7     print "After chaning, in func"
     8     print os.getcwd()
     9 
    10 
    11 if __name__ == "__main__":
    12     print "Before changing, outside func"
    13     print os.getcwd()
    14     chdir_in_func()
    15     print "After changing, outside func"
    16     print os.getcwd()

    The output of this script will be:

    Before changing, outside func
    /home/chdir_in_func
    Before chaning, in func
    /home/chdir_in_func
    After chaning, in func
    /home
    After changing, outside func
    /home

    We can see that in the function, if we changes the directory, the current working directory is changed too.

    A suggested good practice to avoid such unconsciously mistake is that alway change back to your original working directory after the actions done in the new directory, unless you know you need to stay there for next operations. I would strongly recommend that in functions, if you have to change directory, always changes it back before returning:

    def func():
        cwd_save = os.getcwd()
        os.chdir(new_dir)
        # Actions in new_dir
        os.chdir(cwd_save)
        return True
  • 相关阅读:
    Delphi的属性Property
    Delphi数组
    Delphi中record和packed record的区别
    Delphi基本数据类型---枚举、子界、集合、数组
    Delphi的枚举类型
    Java创建线程的细节分析
    java concurrency: ThreadLocal及其实现机制
    java concurrency: daemon线程
    java volatile关键字的理解
    Java动态代理
  • 原文地址:https://www.cnblogs.com/cheese-bacon/p/4150983.html
Copyright © 2011-2022 走看看