[python] hexadecimal conversion

  Programming questions often involve converting the int type into binary and then performing operations. In addition to inventing the while loop on site, is there an easier way to implement it?

1. Convert to binary

1.1 bin function

  bin is python's built-in function that converts int type into binary:

  we only need to intercept based on the return value of the bin function to receive:

>>> a = 7
>>> b = bin(a)[2:]
>>> b
'111'

1.2 format function

  The format function can control the output form of the numbers to be printed, and can be converted to binary through the ":b" method:

>>> a = 7
>>> b = '{0:b}'.format(a)
>>> b
'111'
>>> c = '{:b}'.format(a)
>>> c
'111'

  When converting only a number, the placeholder "0" can be omitted.

1.3 f-string format

  The f-string format is actually a simplified way of writing the format function:

>>> a = 7
>>> b = f'{
      
      a:b}'
>>> b
'111'

2. Convert to octal and hexadecimal

2.1 Octal system

  Octal conversion requires the use of the oct function and the ":o" format:

>>> a = 17

>>> o1 = oct(a)[2:]
>>> o2 = '{0:o}'.format(a)
>>> o3 = f'{
      
      a:o}'

>>> o1 == o2 == o3 == '21'
True

2.2 Hexadecimal

  Hexadecimal conversion requires the hex function and ":x" format:

>>> a = 37

>>> h1 = hex(a)[2:]
>>> h2 = '{0:x}'.format(a)
>>> h3 = f'{
      
      a:x}'

>>> h1 == h2 == h3 == '25'
True

3. Convert back to decimal

  The int function returns decimal by default, and the base parameter needs to be determined based on the number being converted. For example: when converting binary numbers, you need to set base to 2, when converting octal numbers, you need to set base to 8... Among them, "base=" can be omitted.
  Whether to add "0b", "0o" and other prefixes does not affect the result:

>>> int('0b111', base=2)
7
>>> int('0b111', 2)
7
>>> int('111', 2)
7

>>> int('111', 2) == int('0b111', base=2) == 7
True
>>> int('21', 8) == int('0o21', base=8) == 17
True
>>> int('25', 16) == int('0x25', base=16) == 37
True

For more usage methods and applications of python, please pay attention to subsequent updates~