Comparison of Julia and Python

python_julia_comparison.md

Comparison of Julia and Python

Python name	Python meaning	Julia name	Julia meaning
def f(x,y):	named function - duck-typing, no polymorphism	fuction f(x,y)	duck-typing, multiple dispatch to methods
lambda x: x	anonymous function	(x) -> x	anonymous function
class MyClass(Parent)	classical OOP class, multiple inheritance	struct MyStruct{TypeParameters} <: AbstractParent	data and constructor only, types inside struct can be parametrized, can inherit only from abstract types
def __init__(self, x):	constructor of a class, one per class	MyStruct(x) (outer constructor), MyStruct(x) = new(x) (inner constructor)	Constructor method (multiple constructors can be defined, selected using multiple dispatch)
method	function that belongs to a class (single dispatch on first argument self)	method	function implementation for concete parameter types (multiple dispatch on all arguments)
a = MyClass(x), x.func(y)	Creating an object, calling a method defined for its class	a = MyStruct(x), func(x, y)	Creating an object, calling a function on it - func can be specialized both on x and y
module	namespace - defined as a single .py file	module	namespace - defined independenly of file strucutre
package	directory with __init__.py file	NA	directory structure independent of logical structure
package	bundled and installable, e.g. using pip, conda	package	includes dependencies (Project.toml), installable using Pkg, very light-weight
x = 1 if y>0 else -1	conditional assignment	x = y>0 ? 1 : -1	Ternary operator
NA	NA	y>0 && println("y positive"), y>0 || println("y not positive")	short-circuit evaluation
NA	NA	f°g	function compositioning, =(f°g)(x)=f(g(x))
obj.method1().method2()	Chaining of methods	1:10 |> sum |> sqrt	Piping - the output of the previous function is used as input for the following one
@decorator	applies a higher order function to the following def, often used for wrappers	@macro	transformation which has Julia expressions (code) as input and output (very powerful)
with block	context manager, used for opening and teardown of resources	do block	content of the block is passed as anonymous function to function before do statement
raise Exception	raising Exceptions	throw(Exception)	raising Exceptions
try - except - finally	Exception handling, can be used as part of normal program workflow	try - catch - finally	Exception handling, should not be part of normal program workflow due to performance reasons