Reading binary files in Python

Reading binary files means reading data that is stored in a binary format, which is not human-readable. Unlike text files, which store data as readable characters, binary files store data as raw bytes. Binary files store data as a sequence of bytes. Each byte can represent a wide range of values, from simple text characters to more complex data structures like images, videos and executable programs.

Different Modes for Binary Files in Python

When working with binary files in Python, there are specific modes we can use to open them:

• 'rb': Read binary - Opens the file for reading in binary mode.
• 'wb': Write binary - Opens the file for writing in binary mode.
• 'ab': Append binary - Opens the file for appending in binary mode.

Opening a Binary File

To read a binary file, you need to use Python’s built-in open() function, but with the mode 'rb', which stands for read binary. The 'rb' mode tells Python that you intend to read the file in binary format, and it will not try to decode the data into a string (as it would with text files).

file = open("file_name", "rb")

After opening the binary file, you can use different methods to read its content.

Using read()

The open() function is used to open files in Python. When dealing with binary files, we need to specify the mode as 'rb' (read binary) and then use read() to read the binary file.

f = open('example.bin', 'rb')

bin = f.read()
print(bin)

f.close()

Output:

b"b'\\x00\\nNotoSanSha\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\\r\nx00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00LWFNGWp1\\'"

Explanation: This code opens a binary file (example.bin) in read binary mode ('rb'). It reads the entire content of the file into the variable bin as bytes using the read() method. After reading the content, it prints the binary data. Finally, it closes the file using f.close() to release system resources.

Using readlines()

By using readlines() method we can read all lines in a file. However, in binary mode, it returns a list of lines, each ending with a newline byte (b'\n').

with open('example.bin', 'rb') as f:
    lines = f.readlines()
    for i in lines:
        print(i)

Output:

b"b'\\x00\\nNotoSanSha\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\\r\n"
b'x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00LWFNGWp1\\'

Explanation:

• The code opens a binary file (example.bin) in read-binary mode ('rb').
• readlines() reads all lines from the file into a list. Each item in the list is a byte object, representing a line in the binary file.
• The for loop iterates over each line, printing it as it goes.

Reading Binary File in Chunks

Reading a binary file in chunks is useful when dealing with large files that cannot be read into memory all at once. This uses read(size) method which reads up to size bytes from the file. If the size is not specified, it reads until the end of the file.

size = 1024  

with open('example.bin', 'rb') as f:
    while True:
        chunk = f.read(size)
        if not chunk:
            break
        
        print(chunk)

Output:

b"b'\\x00\\nNotoSanSha\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\\r\nx00
\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00LWFNGWp1\\"

Explanation:

• The file example.bin is opened in read-binary mode ('rb').
• The code reads the file in chunks of 1024 bytes using f.read(size).
• The while True loop continues until the file is fully read, breaking when no more data is available (f.read(size) returns an empty chunk). Each chunk is printed to the console.

Related Articles:

• Python | Convert String to bytes
• Python Array
• Read a file line by line in Python
• Reading and Writing a text file in Python