Merge pull request #28 from basnetsoyuj/master

parewa-ranjit · web-flow · commit f61d2b47e711 · 2021-01-20T12:27:18.000+05:45
Added 27-os-module.md
diff --git a/26-file-handling.md b/26-file-handling.md
@@ -1,6 +1,6 @@
 # Python File Handling
 
-**Video link:** 
+**Video link:** [https://youtu.be/crluPcyuchU](https://youtu.be/crluPcyuchU)
 
 In this video, we learned how to perform various file operations like reading and writing into files with the help examples.
 
diff --git a/27-os-module.md b/27-os-module.md
@@ -0,0 +1,153 @@
+# Python `os` module
+
+**Video link:** 
+
+In this video, we learned to use the `os` module to perform various directory operations like creating, renaming, and removing directories with the help of examples. 
+
+**Programs in the Video**
+
+- [Getting Current Directory](#getting-current-directory)
+- [Changing Directory](#changing-directory)
+- [Listing all Directories and Files](#listing-all-directories-and-files)
+- [Making a New Directory](#making-a-new-directory)
+- [Renaming a Directory or a File](#renaming-a-directory-or-a-file)
+- [Removing Directory or File](#removing-directory-or-file)
+
+---
+
+## Getting Current Directory
+We use the `getcwd()` function of the `os` module to get the path to the current directory.
+
+```python
+import os
+
+current_dir = os.getcwd()
+print(current_dir)
+```
+
+When you run the code, the current working directory that is the directory containing our Python file is printed.
+
+---
+
+## Changing Directory
+
+In Python, we can change the current working directory by using the `chdir()` function of the `os` module.
+
+As we saw previously, the present working directory is the directory containing our Python file. Let's change the current working directory
+
+```python
+import os
+
+current_dir = os.getcwd()
+print(current_dir)
+
+os.chdir("/path/new/location")
+print(os.getcwd())
+```
+
+**Output**
+```
+<your file directory location>
+<new location>
+```
+
+>**Note**: Now if we create a file inside the current directory, our file will be created inside `<new location>`.
+
+```python
+import os
+
+current_dir = os.getcwd()
+print(current_dir)
+
+os.chdir("<new location>")
+
+with open("test.txt", "w") as f:
+    f.write("This is a test file.")
+```
+
+We can see the `test.txt` file is created inside the current working directory which is `<new location>`.
+
+---
+
+## Listing all Directories and Files
+
+In Python, all files and sub-directories inside a directory can be retrieved using the `listdir()` function of the `os` module.
+
+For example,
+
+```python
+import os
+
+print(os.listdir())
+```
+
+This function returns a list containing all files and sub-directories in the current working directory.
+
+We can also pass an optional `path` argument to `listdir()` to return files and sub-directories from a specific path.
+
+```python
+import os
+
+print(os.listdir("<path>"))
+```
+
+---
+
+## Making a New Directory
+
+We can create a new directory using the `mkdir()` function of the `os` module.
+
+```python
+import os
+
+os.mkdir("test")
+```
+
+This creates a new `test` directory in our current directory.
+
+---
+
+## Renaming a Directory or a File
+
+We can rename any directory or file using the `os.rename()` function which takes in 2 arguments: `old name` and `new name`.
+
+```python
+import os
+
+# rename directory or file
+os.rename('<old_name>', '<new_name>')
+```
+
+---
+
+## Removing Directory or File
+We can remove a file using the `remove()` function of the `os` module.
+
+```python
+import os
+
+print(os.listdir())
+
+os.remove("<filename>")
+
+print(os.listdir())
+```
+
+After running this code, the file is deleted, so the second `os.listdir()` will not list the file.
+
+---
+
+To remove a directory, we use the `rmdir()` function.
+
+```python
+import os
+
+print(os.listdir())
+
+os.rmdir("<path_to_directory>")
+
+print(os.listdir())
+```
+
+>**Note**: One thing we need to remember when removing a directory is that the directory must be empty. Otherwise, an exception will be raised.
+
