Python Learning note 015--file Common operations binary (binary file)

1-byte (byte) units

1KB = 2*10 Bytes

1MB = 1KB * 1024x768 = 2**20 Bytes

1GB = 1KB * 1K * 1K = 2**30 Bytes

# 1byte = 8bit (bit)

22 Binary files

The binary file is stored in bytes (byte),

File read and write methods that do not differentiate content by line break (\ n)

3 Open Modes Mode

' B '

4-byte String bytes

A byte string is also called a sequence of bytes

Data that is stored in bytes

Immutable byte sequence at byte-string

(If you don't understand it, you can refer to the tuple)

Note:

Byte is an integer between 0~255 (2**8-1) (0b11111111, 0b00000000)

The number of strings stored is the number between 1~65535 (2**16-1) (UNICODE16/UNICODE32)

5 Creating a byte string

In non-special cases, single and double quotes have the same effect when creating a string

5.1 Creating an empty byte string

There are two ways of creating an empty string

Mode 1:

>>> B = b"">>> bb">>> b = B" ">>> BB "'

Mode 2:

>>> D = bytes ()>>> Db"

5.2 Creating a non-empty byte string

>>> A = b"ABCD">>> B = b"ABCD">>> C = b" "ABCD" ">>> d = b'\x41\x42'>>>AB'ABCD'>>>BB'ABCD'>>>CB'ABCD'>>>DB'AB'

Construct (create) function for 6-byte string bytes

bytes () : Creates an empty byte string, equivalent to B '
bytes (integer-iterated object) : Initializes a byte string with an iterative object (the value must be an integer of 0~255)
bytes (integer n) : Generates n byte strings with a value of 0
bytes (string, encoding= ' Utf-8 ') : Generates a byte string with the conversion encoding of strings

Example

>>> B = bytes (Range (0x41,0x41+26))>>>BB'abcdefghijklmnopqrstuvwxyz'>>> c = Bytes (4)>>>CB'\x00\x00\x00\x00'>>> e = bytes ("python",'ASCII')>>>EB'python'>>> f = bytes ("English",'Utf-8')>>>FB'\xe4\xb8\xad\xe6\x96\x87'

Operation of 7-byte string

+  +=  *   *=

Comparison operations: < <= > >= = = =!

In/not in operator

Indexed index

Sliced slice

82 Write operations example for a binary file

Python Learning note 015--file Common operations binary (binary file)