A learning series of Python , Day-2

What is Identifier ? A name in python program is known as Identifier / Reference variable /variable A used-defined name to discribe something to machine. Rules of declaring Identifiers Starts with alphabets[lowerCase / upperCase ] Digits are permitted , but should not starts with digits Using UnderScore(_) -Should not to use reserved Keywords ###Valid Identifiers Name = "Ajay" name = "Ajay" name1 = Ajay" newName = "Ajay" New_name = "Ajay" _Name = "Ajay" __Name = "ajay" __name__ = "ajay" Enter fullscreen mode Exit fullscreen mode ###Invalid Indentifers 1name = "ajay" new name = "ajay" class ="ajay" # class is the reserved keyword new-Name = "ajay" Enter fullscreen mode Exit fullscreen mode Rule of UnderScore in Python _name --->(#private): A single underscore indicates that a variable or method is intended for internal use. Please treat this as internal class Student: def __init__(self): self._marks = 90 s = Student() print(s._marks) Enter fullscreen mode Exit fullscreen mode __name --->(#Strictly private): A double underscore before a name triggers name mangling. Python changes the attribute's internal name to reduce accidental access and naming conflicts. Reduce accidental access and naming conflicts class Student: def __init__(self): self.__marks = 90 s = Student() # print(s.__marks) # AttributeError print(s._Student__marks) Enter fullscreen mode Exit fullscreen mode name --->(Special methods): Double underscores on both sides identify special names used by Python. They are often called dunder names. Python special method or attribute class Student: def __init__(self, name): self.name = name def __str__(self): return self.name s = Student("Ajay") print(s) Enter fullscreen mode Exit fullscreen mode Reserved Words Reserved words are known as keywords are predefined, case Senstive identifier used in language to fidn the syntax and structure. Reserved words should not be an identifies , function , object 30+ keywords in python Reserved words are... ['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']