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Python Reading from and writing to files

Reading from and writing to files in Python is straightforward and can be accomplished using the built-in open() function. Here's a basic guide to help you get started:

Reading from a File

  1. Open the File: Use open() to open the file. You can specify the mode as 'r' for reading.
  2. Read the File: Use methods like read(), readline(), or readlines() to read the file contents.
  3. Close the File: Always close the file using close() to free up system resources.
Here's an example of reading the entire content of a file:

# Open the file in read mode
with open('example.txt', 'r') as file:
    # Read the contents of the file
    contents = file.read()

# Print the contents
print(contents)


Writing to a File

  1. Open the File: Use open() with mode 'w' for writing, 'a' for appending, or 'w+' for reading and writing.
  2. Write to the File: Use methods like write() or writelines() to write data to the file.
  3. Close the File: Close the file using close().

Here's an example of writing to a file:

# Open the file in write mode with open('example.txt', 'w') as file: # Write some text to the file file.write('Hello, world!') # If you want to append to the file, use 'a' mode with open('example.txt', 'a') as file: # Append some text to the file file.write('\nAppended text.')


Using with Statement

Using the with statement is a good practice as it automatically closes the file for you, even if an exception occurs.

Full Example: Reading and Writing

Here’s a full example demonstrating both reading from and writing to a file:

# Write to the file with open('example.txt', 'w') as file: file.write('Hello, world!\n') file.write('This is a test file.\n') # Read from the file with open('example.txt', 'r') as file: contents = file.read() print(contents)


Common File Modes

  • 'r': Read (default mode). Opens the file for reading.
  • 'w': Write. Opens the file for writing (creates a new file or truncates the existing file).
  • 'a': Append. Opens the file for appending (creates a new file if it doesn't exist).
  • 'r+': Read and write. Opens the file for both reading and writing.
  • 'w+': Write and read. Opens the file for writing and reading (creates a new file or truncates the existing file).
  • 'a+': Append and read. Opens the file for appending and reading (creates a new file if it doesn't exist).

By using these simple techniques, you can easily read from and write to files in Python.

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