Discover and read the best of Twitter Threads about #TerminologyTuesday
Most recents (10)
Python class curious? ๐ค
Here's a 4-in-1 thread about class-related Python terms ๐
โข class
โข class instance
โข method
โข initializer method
Make sure to click through to each of the 4 thread for more ๐งต
#Python #TerminologyTuesday
Here's a 4-in-1 thread about class-related Python terms ๐
โข class
โข class instance
โข method
โข initializer method
Make sure to click through to each of the 4 thread for more ๐งต
#Python #TerminologyTuesday
A class is essentially a template for creating an object in Python.
Every object has a class, seen by the "type" function:
>>> type(4)
<class 'int'>
The terms "type" & "class" are synonyms in Python.
Some "functions" are actually implemented as classes.
On ๐ฐ๐น๐ฎ๐๐๐ฒ๐ ๐ฑ๏ธ
Every object has a class, seen by the "type" function:
>>> type(4)
<class 'int'>
The terms "type" & "class" are synonyms in Python.
Some "functions" are actually implemented as classes.
On ๐ฐ๐น๐ฎ๐๐๐ฒ๐ ๐ฑ๏ธ
Calling a class returns an "instance" of that class.
All objects are instances of their "type".
>>> x = True
>>> type(x) == bool
True
>>> isinstance(x, bool)
True
But objects are instances of parent classes as well:
>>> isinstance(x, int)
True
On ๐ถ๐ป๐๐๐ฎ๐ป๐ฐ๐ฒ๐ ๐ฑ๏ธ
All objects are instances of their "type".
>>> x = True
>>> type(x) == bool
True
>>> isinstance(x, bool)
True
But objects are instances of parent classes as well:
>>> isinstance(x, int)
True
On ๐ถ๐ป๐๐๐ฎ๐ป๐ฐ๐ฒ๐ ๐ฑ๏ธ
What's "assignment" in #Python?
This might seem like a simple concept, but there are some gotchas in the way assignment works in Python.
Fundamentally "assignment" describes the action of binding a name to a value.
This might seem like a simple concept, but there are some gotchas in the way assignment works in Python.
Fundamentally "assignment" describes the action of binding a name to a value.
You can assign a variable (a.k.a. name) to a value (a.k.a. object) with an "assignment statement".
That uses an = sign, like this:
>>> x = []
That assigns the name x to an empty list.
If "x" already exists, an = sign will re-assign it to a new value:
.>>> x = 4
>>> x
4
That uses an = sign, like this:
>>> x = []
That assigns the name x to an empty list.
If "x" already exists, an = sign will re-assign it to a new value:
.>>> x = 4
>>> x
4
Python programmers often talk about names "binding" to objects or variables "pointing" to objects.
In Python, variables point to (or "refer to") values. Variables don't *contain* objects, but just say "look over there for the object". ๐
Beware of code like this:
x = []
y = x
In Python, variables point to (or "refer to") values. Variables don't *contain* objects, but just say "look over there for the object". ๐
Beware of code like this:
x = []
y = x
What's a "generator" in Python?
#TerminologyTuesday time โฐ
Let's discuss:
โข The main reason generators are used
โข The 2 ways to make a generator
โข Lesser known generator features
โข Why and when to use generators
Thread ๐งต๐
#TerminologyTuesday time โฐ
Let's discuss:
โข The main reason generators are used
โข The 2 ways to make a generator
โข Lesser known generator features
โข Why and when to use generators
Thread ๐งต๐
Generators are typically used as lazy iterables.
By "lazy" I mean that they don't actually compute their values until they absolutely need to.
Essentially generators will "generate" their next value as soon as they're asked for it.
By "lazy" I mean that they don't actually compute their values until they absolutely need to.
Essentially generators will "generate" their next value as soon as they're asked for it.
Here's a generator of every .py file in my home directory:
>>> from pathlib import Path
>>> py_files = Path.home().rglob("*.py")
>>> py_files
<generator object Path.rglob at 0x7f5a6721c900>
(the rglob method on pathlib.Path objects always returns a generator)
>>> from pathlib import Path
>>> py_files = Path.home().rglob("*.py")
>>> py_files
<generator object Path.rglob at 0x7f5a6721c900>
(the rglob method on pathlib.Path objects always returns a generator)
What's a regular expression (a.k.a. regex)? ๐ค #TerminologyTuesday
Yes, they're a programming language within a programming language that's just for pattern matching and they're extremely succinct.
But what does "regular expression" really mean? And where did they come from?
Yes, they're a programming language within a programming language that's just for pattern matching and they're extremely succinct.
But what does "regular expression" really mean? And where did they come from?
Haven't seen regular expressions?
Imagine a special purpose programming language where every single character is a statement and no whitespace or comments are allowed. ๐จ
Regular expressions are extremely information dense but very helpful for certain types of pattern matching.
Imagine a special purpose programming language where every single character is a statement and no whitespace or comments are allowed. ๐จ
Regular expressions are extremely information dense but very helpful for certain types of pattern matching.
Regular expressions are called "regular" because regular expressions define a "regular language".
What's a "regular language"?
I'm so glad you asked! This is one of the few factoids from my CS degree that actually stuck with me.
This part of CS is tightly tied to linguistics.
What's a "regular language"?
I'm so glad you asked! This is one of the few factoids from my CS degree that actually stuck with me.
This part of CS is tightly tied to linguistics.
What's an "object" in Python?
According to the Python glossary, an object is:
> Any data with state (attributes or value) and defined behavior (methods). Also the ultimate base class of any new-style class.
What does that really mean? (thread๐งต)
#Python #TerminologyTuesday
According to the Python glossary, an object is:
> Any data with state (attributes or value) and defined behavior (methods). Also the ultimate base class of any new-style class.
What does that really mean? (thread๐งต)
#Python #TerminologyTuesday
Usually when we think of an "object" we think of class instance. For example these are all objects:
>>> numbers = [2, 1, 3, 4, 7] # a list object
>>> colors = {"red", "green", "blue", "yellow"} # a set object
>>> name = "Trey" # a string object
>>> n = 3 # an int object
>>> numbers = [2, 1, 3, 4, 7] # a list object
>>> colors = {"red", "green", "blue", "yellow"} # a set object
>>> name = "Trey" # a string object
>>> n = 3 # an int object
Anything that can have attributes is an object.
Anything that can has methods is an object.
Anything that you can point a variable to is an object.
Pretty much EVERY THING is an object in Python.
Anything that can has methods is an object.
Anything that you can point a variable to is an object.
Pretty much EVERY THING is an object in Python.
class: a template for creating an object
We've defined instance and method. For this week's #TerminologyTuesday, it's finally time to define the word "class" in #Python. ๐๐
Where do classes come up and how do they work? ๐ค
We've defined instance and method. For this week's #TerminologyTuesday, it's finally time to define the word "class" in #Python. ๐๐
Where do classes come up and how do they work? ๐ค
The terms "class" and "type" are synonyms in Python.
The type of an object is its class and an object's class is a "type".
As we discussed when we defined "class instance" last week, every object in Python has a class. That means classes are EVERYWHERE in Python.
The type of an object is its class and an object's class is a "type".
As we discussed when we defined "class instance" last week, every object in Python has a class. That means classes are EVERYWHERE in Python.
list, dict, int, str, tuple, bool, set, and float are all classes.
But (somewhat strangely) range, enumerate, zip, reversed, and type are also classes. ๐ฆ Huh?
We often don't care whether an object is a class or a function in Python. Both are callables. ๐
But (somewhat strangely) range, enumerate, zip, reversed, and type are also classes. ๐ฆ Huh?
We often don't care whether an object is a class or a function in Python. Both are callables. ๐
instantiate (verb): to make an "instance" of a class
Okay... but what's an "instance"? ๐ค
instance (noun): an object
Wait, that's not a helpful definition.
Let's talk about class instances and class instantiation in Python.
#TerminologyTuesday
Okay... but what's an "instance"? ๐ค
instance (noun): an object
Wait, that's not a helpful definition.
Let's talk about class instances and class instantiation in Python.
#TerminologyTuesday
You can think of a "class" as a blueprint for making an objects that have specific functionality and contain particular types of data. ๐
list is a class in #Python
>>> list
<class 'list'>
An "instance of the list class" could also be called a "list object" or just "a list".
list is a class in #Python
>>> list
<class 'list'>
An "instance of the list class" could also be called a "list object" or just "a list".
So instances of the list class (a.k.a. "lists") share their functionality with other list instances.
Here's 2 list instances:
>>> a = []
>>> b = []
They each have the same methods:
>>> a.append(2)
>>> b.append(5)
But they store separate data:
>>> a
[2]
>>> b
[5]
Here's 2 list instances:
>>> a = []
>>> b = []
They each have the same methods:
>>> a.append(2)
>>> b.append(5)
But they store separate data:
>>> a
[2]
>>> b
[5]
Another fundamental Python term for #TerminologyTuesday
callable: an object which can be called
The classical "callable" is a function, but in #Python classes are also callables.
callable: an object which can be called
The classical "callable" is a function, but in #Python classes are also callables.
In many programming languages (e.g. JS, PHP, C++) creating a new "instance" of a class (an object whose type is that class) involves the "new" keyword:
let eol = new Date(2020, 1, 1);
But in #Python to make a new class instance we just call the class:
eol = date(2020, 1, 1)
let eol = new Date(2020, 1, 1);
But in #Python to make a new class instance we just call the class:
eol = date(2020, 1, 1)
The fact that classes are callables means the distinction between a function and a class is often quite subtle. All of these "functions" are actually implemented as classes:
n = float("4.5")
m = int(n)
s = str(m)
b = bool(m)
t = tuple('abcd')
e = enumerate(t)
r = reversed(t)
n = float("4.5")
m = int(n)
s = str(m)
b = bool(m)
t = tuple('abcd')
e = enumerate(t)
r = reversed(t)
Ever wondered "what's a float"?
floating point number (a.k.a. float): an object used for representing real numbers using a fairly accurate approximation
Let's talk about floats work in #Python!
#TerminologyTuesday
floating point number (a.k.a. float): an object used for representing real numbers using a fairly accurate approximation
Let's talk about floats work in #Python!
#TerminologyTuesday
Floating point numbers are an approximation of their decimal equivalents.
They're super useful for most uses, but they can't be relied on for exact precision.
You can't assume that an exact equality comparison with floating point numbers will work:
>>> 0.1 + 0.02 == 0.12
False
They're super useful for most uses, but they can't be relied on for exact precision.
You can't assume that an exact equality comparison with floating point numbers will work:
>>> 0.1 + 0.02 == 0.12
False
Adding 0.1 and 0.02 results in a number that is VERY slightly different from the 0.12 number that we'd expect:
>>> 0.1 + 0.02
0.12000000000000001
This might seem like a huge problem, but it's usually not! This imprecision typically only causes trouble with strict equality.
>>> 0.1 + 0.02
0.12000000000000001
This might seem like a huge problem, but it's usually not! This imprecision typically only causes trouble with strict equality.
Here's a deceptively fuzzy #Python term: mutable object. ๐ค
mutable object: an object whose "value" can change
But what does "value" really mean?
#TerminologyTuesday
mutable object: an object whose "value" can change
But what does "value" really mean?
#TerminologyTuesday
Lists are mutable because a list object can be changed.
>>> numbers = [2, 1, 3]
>>> numbers.append(4)
>>> numbers
[2, 1, 3, 4]
If two variables refer to the same list, any change to the list will be reflected by both variables:
>>> x = numbers
>>> x.clear()
>>> numbers
[]
>>> numbers = [2, 1, 3]
>>> numbers.append(4)
>>> numbers
[2, 1, 3, 4]
If two variables refer to the same list, any change to the list will be reflected by both variables:
>>> x = numbers
>>> x.clear()
>>> numbers
[]
Strings are immutable in #Python. That means that there is no way to "change" a string object in Python.
Try as hard as you might, you cannot change strings. You can only make NEW strings.
name = "Trey"
name = name + "!" # makes a new string
name += "!" # same as above
Try as hard as you might, you cannot change strings. You can only make NEW strings.
name = "Trey"
name = name + "!" # makes a new string
name += "!" # same as above
