Files

Introduction to File Handling in Python

• Overview of file handling concepts in Python

• Importance of reading and writing to files outside the Python environment

Types of Files

• Example of plain text file with English text

• Can be opened using TextEdit (macOS) or Notepad (Windows)

• Contains unformatted text

Opening Files

• Use the open() function to open a file

• Syntax: open("filename.txt", "mode")

  • filename: name of the file

  • mode: indicates the operation type

• Common modes:

  • "r": open for reading (default mode)

  • "w": open for writing (truncate existing content)

  • "a": open for appending (write at the end of the file)

Reading Files

• Store the return value of open() in a variable (e.g., file)

• The read() method:

  • Use file.read(n) to read the next n characters

  • Use file.read() without arguments to read the entire file

• Empty string returned when end of file is reached

• Remember to close the file using file.close()

Reading Lines

• Use readline() to read one line at a time:

  • Each call to file.readline() retrieves the next line

  • Each line ends with a newline character (\n)

• Strip newline characters using strip() method

Writing Files

• To create a new file or overwrite an existing one, use open("newfile.txt", "w")

• Writing text using file.write("text")

• NN: If needing new lines, include \n within the write string

• Always close the file after writing with file.close()

Modes of Writing

• Opening a file in "w" mode truncates existing content

• To append content without deleting existing data, use "a" mode

  • New content is added to the end of the file

Example Demonstration

• Create a file called hello.txt

  • Write "hello
    " followed by "world
    "

• Check file contents to see proper line placement

Conclusion

• Recap of file operations: opening, reading, writing, and appending

• Highlight the importance of closing files in programming