File Handling Modes and Types

• A file is a collection of bytes stored on a storage device like a hard disk or thumb drive.

File Handling Modes

• r: Read mode, used for reading files; the file must exist.
• rb: Read binary mode, used for reading binary files; needed to work with non-text files.
• w: Write mode, used for writing files; creates a new file or overwrites an existing one, so use with caution.
• wb: Write binary mode, used for writing binary files, overwrites or creates the file.
• a: Append mode, used for adding data to the end of a file, preserves existing content.
• ab: Append binary mode, used for appending data to a binary file.
• r+: Read and write mode, requires the file to already exist.
• rb+: Read and write mode for binary files.
• w+: Write and read mode, truncates the existing file or creates a new one.
• wb+: Write and read mode for binary files.
• a+: Append and read mode, creates a new file or appends to an existing one.
• ab+: Append and read mode for binary files.

File Types

• Data Files: General category that includes both text and binary files.
• Text Files:
  • Structured as a sequence of lines, with each line being a sequence of characters.
  • Each line ends with a special End of Line (EOL) character.
  • Store information in ASCII or Unicode characters.
• Binary Files:
  • Files where the format is not made of readable characters.
  • Can include images (JPEG, GIF), audio (MP3), documents (Word, PDF), etc.
  • Contents are raw data, with no translation occurring.
  • Faster for programs to read and write than text files.
  • To open files in binary mode you must add 'b' to the mode
• CSV Files:
  • Comma Separated Values file, used to store tabular data.
  • A delimited text file that uses a comma to separate values.
  • Each line is a data record, and each record contains one or more fields, separated by commas.

File Operations

• Opening a file:
  • A file object (or handle) is created using the open() method.
  • Syntax: file = open("filename.txt", "mode")
• Closing a file:
  • An open file should be closed using the close() method.
  • Syntax: file.close()
• Reading from files:
  • read(): Reads at most n bytes; if n is not specified, reads the entire file.
  • readline(): Reads a line of input; if n is specified, reads at most n bytes, useful for reading line by line.
  • readlines(): Reads all lines and returns them in a list.
• Writing to files:
  • write(str): Writes the string str to the file.
  • writelines(list): Writes all strings in a list L as lines to the file.
• Reading operation: read(), readline(), readlines()
• Writing operation: write(), writelines()

Processing Files

• Steps to process a file involve opening it, processing the data, and then closing it.

Absolute and Relative Paths

• Absolute Path: Specifies the exact location of a file, including the drive label and all directories.
• Relative Path: Specifies the location of a file relative to the current working directory.

Using the with Clause

• The with statement can be used to automatically close files, even if exceptions occur.
• Syntax: with open("filename.txt", "r") as file:.

File Mode

• Defines how the file will be accessed.
• Includes read, write, append, and their combinations.

Other Functions

• flush(): Forces the writing of data on disc which was still pending in the output buffer.
  • Syntax: <file_object>.flush()
• seek(): Changes the position of the file pointer.
  • Syntax: <file_object>.seek(offset, mode)
  • offset: The offset indicates the number of positions to move the file pointer.
  • mode:
    • 0: beginning of the file
    • 1: current position of file pointer
    • 2: end of file
• tell(): Returns the current position of the file pointer.
  • Syntax: <file_object>.tell()

Working with Binary Files

• Binary files store information as a stream of bytes.
• Require specific modes (rb, wb, ab, etc.) for reading and writing.
• No delimiter for a line
• No translation occurs
• Pickle module is used to work with complex Python Objects

Pickle Module

• Used to serialize and de-serialize Python object structures.
• Converts Python objects (lists, dictionaries, etc.) into byte streams.
• dump(): Writes the pickled object to a file.
  • Syntax: pickle.dump(structure, file_object)
• load(): Reads the pickled object from a file.
  • Syntax: structure = pickle.load(file_object)

Key Differences Between Binary Files and Text Files

• Nature of Data:
  • Binary files store data in binary format (0s and 1s) and not human-readable.
  • Text files store data in a human-readable format, using characters encoded in ASCII or Unicode.
• Usage:
  • Binary files are used for media files, compiled programs, and serialization.
  • Text files are used for source code, configuration files, and documents.
• Encoding:
  • Binary files have no specific encoding scheme.
  • Text files use encoding schemes like ASCII, UTF-8, or UTF-16.