Didn’t call super() __init__ in your Python class? Attributes normally set on the parent won’t be on the child! The post Python inheritance: Skipping super().__init__ loses parent attributes appeared first on LernerPython.

The most common place we use super() in Python? __init__: The post Python super().__init__: Passing arguments to the parent class appeared first on LernerPython.

Misspelled the method you invoke via super() in a Python method? It’s a runtime error: We get: AttributeError: ‘super’ object has no attribute ‘y’ The post Python super(): Misspelled method names raise AttributeError appeared first on LernerPython.

A Python method can invoke a method in the parent class with super(): super() doesn’t invoke the method. It’s a proxy on which you invoke the method you want. The post Python’s super(): A proxy for calling parent-class methods appeared first on LernerPython.

If a Python subclass defines a method with the same name as the parent, the parent’s method isn’t invoked: The post Python method overriding: Child methods replace the parent’s appeared first on LernerPython.

I just got back from PyCon US. It was delightful; I saw old friends, met new ones, gave a tutorial on decorators, and spoke at the education summit. I’m a […] The post Is Python becoming Pinyin? appeared first on LernerPython.

Thanks to ICPO/MRO, if a child Python class doesn’t define a method, the parent method will be invoked: The post Python method resolution order: Inheriting methods from a parent appeared first on LernerPython.

Inheritance in Python changes the attribute lookup path, aka the “method resolution order,” or MRO: Child.__mro__ # (__main__.Child, object) Child.__mro__ # (__main__.Child, __main__.Parent, object) The post Python method resolution order: Reading a class’s __mro__ appeared first on LernerPython.

Set one Python class to inherit from another by putting the parent in (): Child.__bases__ # who does Child inherit from? The post Python class inheritance: Subclassing, __bases__, and isinstance appeared first on LernerPython.

Python uses attributes where other languages use different terms (and data structures): – Instance variable — attribute on an instance (self)– Class variable — attribute on a class– Method — […] The post Python attributes: Instance variables, class variables, and methods appeared first on LernerPyth...

Python methods are stored on a class, not an instance. Given x.m(), how does Python find it? The ICPO rule: – First, look for an attribute on the _i_nstance.– Not […] The post Python attribute lookup: The ICPO rule for finding methods appeared first on LernerPython.

By default, every Python class inherits from “object”. You can see this by checking the __bases__ attribute on a class: __bases__ is a tuple — hinting (correctly) that Python supports […] The post Python `__bases__`: Every class inherits from object appeared first on LernerPython.

Creating a Python class? You’re already using composition, the has-a relationship. How? When you assign to an attribute (e.g., self.name = name) in a Person class, you’re saying, “Person has-a […] The post Composition in Python classes: The has-a relationship appeared first on LernerPython.

Writing object-oriented Python? Don’t confuse the two core relationships: – has-a (“composition”). One object contains another. A Person has-a name. A Car has-a color.– is-a (“inheritance”). One class is similar […] The post Python composition vs inheritance: The has-a and is-a relationships appeare...

Python’s ternary operator is convenient, but easy to abuse: ‘A’ if s>=90 else ‘B’ if s>=80 else ‘C’ if s>=70 else ‘F’ Just because you CAN, doesn’t mean you SHOULD! […] The post Python ternary operator: When to use if-elif-else instead appeared first on LernerPython.

Want an if-else statement in your Python lambda? You can’t because it’s a statement. Instead, use the ternary operator: In other words: If it’s a string, return the value. If […] The post Python lambda if-else: Use the ternary operator instead appeared first on LernerPython.

In yesterday’s post, you saw Python’s ternary operator (an if-else expression). It’s useful in lambdas and comprehensions: VALUE_IF_TRUE if CONDITION else VALUE_IF_FALSE For example: The post Python’s ternary operator: Conditional expressions in comprehensions appeared first on LernerPython.

Defining a custom __format__ method in Python? Go bananas, if you want. For example (see image for full demo): The post Python `__format__`: Define your own format specification syntax appeared first on LernerPython.

Defining __format__ in a Python class? Check if the second argument is ”, meaning no format code: The post Python __format__: Detecting an empty format code appeared first on LernerPython.

Want your Python class to take custom format codes? Define __format__. This method returns self.x *except* with a :< format. Then it reverses self.x: The post Python `__format__`: Custom format codes for your own classes appeared first on LernerPython.

A Python value x in an f-string’s {} normally interpolates str(x), aka x.__str__. Want the repr instead, aka x.__repr__? Put !r after the value: f'{x}’ # returns str(x)f'{x!s}’ # also […] The post f-string conversion flags: Using !r to get repr instead of str appeared first on LernerPython.

Have a Python datetime, and want to print it? Use an f-string, and pass a strftime-style format: f'{now:%Y-%m-%d}’ # year-month-datef'{now:%Y-%m-%d %H:%M:%S}’ # year-month-date hour:min:sec # Easily integrate into user outputf’Today […] The post Formatting a Python datetime with f-strings and strfti...

Have a Python number, and want commas before every 3 digits? Use , in an f-string: Floats, too: Combine , and .2f: The post Thousands separators in Python f-strings: Format with commas appeared first on LernerPython.

Have a Python float, and want to show it as a percentage? Use % in an f-string The post Python float to percentage: Format with % in an f-string appeared first on LernerPython.

Want to display a Python float with a limited number of decimals? Use .nf as an f-string’s format specifier. n is the number of digits to show after the decimal: […] The post Formatting floats in Python f-strings: The .nf specifier appeared first on LernerPython.

Use Python f-strings and format specifiers to make quick-and-dirty tables: Output: a…….10bcd……2e…..3456 The post Python f-string format specifiers: Padding and aligning columns appeared first on LernerPython.

A Python f-string can have a “format specifier,” one or more characters after : that dictate the format. For example, you can use < ^ and > with an integer […] The post Python f-string format specifiers: Aligning and padding text appeared first on LernerPython.

Want to print a Python expression and its value? The modern way: All expressions work: The post Python f-string debugging: Printing expressions with = appeared first on LernerPython.

Remember, Python f-strings are strings: 1. Use f-strings anywhere you’d use strings, e.g., filenames and URLs2. You don’t have to print an f-string; you can store it.3. Don’t overuse them! […] The post Python f-strings are just strings: Use them anywhere appeared first on LernerPython.

Python f-strings are the best: – Put an f before the opening ‘ or “– Creates a regular string– Expressions in {} are evaluated/interpolated The post Python f-strings: Embedding expressions inside strings appeared first on LernerPython.