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'const'

Const basically makes data "Read-Only". Its an important feature to help prevent developers from changing data they were not supposed to, and to informing other developers that data marked const will not change.

Python Qt/Cpp
  1. # Special thanks from jinsuun__ on #python irc
  2. from dataclasses import dataclass
  4. @dataclass
  5. class C:
  6. m_c: int
  7. isLetter : bool = False
  8. isNonCharacter : bool = False
  9. isNull : bool = False
  10. isNumber : bool = False
  11. isPrintable : bool = True
  12. isSpace : bool = False
  13. isUpper : bool = False
  14. n = 88
  15. c = C(n)
  17. match c:
  18. case C(0):
  19. c.isNull = True
  20. case C( m_c = x ) if x in range( 1, 32 ) or x == 127:
  21. c.isNonCharacter = True
  22. c.isPrintable = False
  23. case C(" "):
  24. c.isSpace = True
  25. case C(x) if x in range( ord("A"), ord("Z") + 1 ):
  26. c.isUpper = True
  27. c.isLetter = True
  28. case C(x) if x in range( ord("a"), ord("z") + 1 ):
  29. c.isUpper = False
  30. c.isLetter = True
  31. case C(x) if x in range( ord("0"), ord("9") + 1 ):
  32. c.isNumber = True
  33. case _:
  34. pass
  1. qint8 c(88);
  2. bool isLetter (false);
  3. bool isNonCharacter(false);
  4. bool isNull (false);
  5. bool isNumber (false);
  6. bool isPrintable (true );
  7. bool isSpace (false);
  8. bool isUpper (false);
  10. switch (c) {
  11. default: break;
  12. case 0 :
  13. isNull = true;
  14. [[fallthrough]];
  15. case 1 ... 31:
  16. case 127 : // Delete
  17. isNonCharacter = true;
  18. isPrintable = false;
  19. break;
  21. case ' ':
  22. isSpace = true;
  23. break;
  25. case 'A' ... 'Z':
  26. isUpper = true;
  27. [[fallthrough]];
  28. case 'a' ... 'z':
  29. isLetter = true;
  30. break;
  32. case '0' ... '9':
  33. isNumber = true;
  34. break;
  35. }
Read as:
  • [ Something identified as ] 'sneed' [which may or may not already exist]
  • finally [ but not really finally ] equals "feed" [ implying that sneed is a string type ].
  • A [ new ] constant string 'sneed'
  • is [ initialized as ] "feed".
Benefits:
  • mypy will tell you that this variable 'shouldnt' be reassigned.
  • Code can not be compiled if you try to overwrite sneed.
  • Standard practice.
  • Part of the language.
Drawbacks:
  • You have to install mypy.
  • Variable is not readonly.
  • `sneed: Final = "feed"` can colliqually referred to as an "east const".
  • Not standard practice.
  • Not part of the language.
  • None.

Final Thoughts