These are “Dunder” (Double Underscore) Methods & Variables, mainly used for special functions and attributes in Python.
| Dunder Name | Purpose |
|---|
__init__ | Constructor method in classes |
__str__ | String representation (str(obj)) |
__repr__ | Debug representation (repr(obj)) |
__name__ | Module name (__name__ == "__main__") |
__call__ | Make an object callable (obj()) |
__len__ | Length of an object (len(obj)) |
__getitem__ | Indexing support (obj[key]) |
__setattr__ | Control setting attributes |
__del__ | Destructor method |
__new__ | Customize object creation |
- These are not “keywords”, but rather special names recognized by Python.
These are called “Decorators”, which modify functions or methods.
| Decorator | Purpose |
|---|
@decorator | Defines a decorator function |
@classmethod | Defines a class method |
@staticmethod | Defines a static method |
@property | Defines a getter property |
@app.route() | Flask route decorator (e.g., @app.route("/")) |
@pytest.mark | Pytest test marker |
- Decorators start with
@ and modify functions/classes.
| Prefix | Meaning | Example |
|---|
f"" or f''' | Formatted String Literal (f-strings) | name = "Gaurav"; print(f"Hello {name}") → "Hello Gaurav" |
r"" or r'' | Raw String (ignores escape sequences) | print(r"C:\new\folder") → "C:\new\folder" |
b"" or b'' | Byte String | b"hello" → b'hello' |
u"" | Unicode String (Python 2, redundant in Python 3) | u"hello" → "hello" |
""" or ''' | Multiline String | """Hello\nWorld""" → "Hello\nWorld" |
% Formatting | Old String Formatting | "Hello %s" % "Gaurav" |
.format() | String format() method | "Hello {}".format("Gaurav") |
f"" → Best for dynamic formatting (faster & readable).r"" → Best for regex or Windows paths (avoids \n issues).b"" → For byte data, encoding purposes.""" """ → For docstrings & multi-line text.