Manav Goyal

File Handling - Python

OS Module
- import os => Import module
- os.mkdir("folderPath") => Creates a folder in the current directory
  - If folder already exists then gives error
- varName = open("filePath", os.O_RDONLY) => Open file in read only mode
- varName = open("filePath", os.O_WRONLY) => Open file in write only mode
- varName1 = os.read(varName, 1024) => Read contents of the file
- os.close() => Close the file
- os.path.exists("filePath") => Returns true of file/folder exists
- os.rename("sourceFilePath", "destinationFilePath") => Renames
- os.listdir("folderPath") => Returns list of folders
- os.getcwd()
- os.system("date")
Shutil Module
File handling
- varName = open("fileName", "r") => Open file in reading mode, Gives error if file does not exist
  - varName = open("fileName") => Default mode is reading
  - varName1 = varName.read() => Gets content of the file
- varName = open("fileName", "w") => Open file in writing mode, Creates a new file if it does not exist
  - varName.write("value") => Write in file, Needs to close the file
- varName = open("fileName", "a") => Appending in file, Creates a new file if it does not exist
  - varName.write("value") => Appends in file
- varName = open("fileName", "x") => Creates file, Gives error if it already exist
- varName = open("fileName", "rt") => Used to handle text file, Default is this mode
  - varName = open("fileName", "wt")
- varName = open("fileName", "rb") => Used to handle binary files, Images, PDFs
- varName.close() => Closes the opened file
- No need to close manually
```
    with open("fileName", "w") as f:
        f.write("value")
        f.truncate(N) # Truncates the file to specified size
```
- Seek => Allows you to move the current position within the file to a specific point, Position is specified in bytes
```
    with open("fileName", "r") as f:
        f.seek(N) # Move to Nth byte in file
        varName = f.read(N) # Read the next N bytes
        f.tell() # Returns the current position within the file in bytes
```