Python vs JS Cheatsheet

This cheat-sheet is handy for all of you who throttle between python and javascript

None

None # python
null // javascript

else if

if val == 0: # python
    pass
elif val == 1:
    pass
else
    pass

if (val == 0) { // javascript
}
else if (val == 1) {
}
else {
}

Type testing

if isinstance(test, bool) // python
if (typeof test === 'boolean') // javascript

Type conversions

some of them

st = str(i) // python
let st = i.toString() // javascript

i = int(st) // python
let i = parseInt(st) // javascript

Strings

append

st = st + 'more' # python
st = st.concat('more') // javascript

length

len(st) # python
st.length // javascript

interpolation

'kikkelis-kokkelis-{parameter}'.format(parameter=1) # python
f'kikkelis-kokkelis-{parameter} # python
`kikkelis-kokkelis-${parameter}" // javascript

splitting

str.split(",") // python AND javascript

substring check

substring in string # python
string.includes(substring) // javascript

Lists, Arrays

iteration

for item in lis: # python
    <code>
list.forEach(item => { // javascript
    <code> // NOTE: if you need early termination, don't use forEach
})
for (const item of lis) { // javascript
    <code>
}
for i, item in enumerate(lis): # python
    <code>
for (var i = 0; i < list.length; i++) { // javascript
    var item = list[i]
    <code>
}

creation

lis = [] # python
lis.append(item)
var lis = [] // javascript
lis.push(item)

modification

lis.pop(index) # python
lis.splice(index, 1) // javascript

find index

lis.index(element) # python
lis.indexOf(element) // javascript

Sets

from a list

s = set(lis) # python
s = Set(lis) // javascript

args

def func(*args): # python
    pass # args is a list
function func(...args) { // javascript
    // args is an array
}

Dictionaries, Objects

creating

dic = {} # python
dic = Objects() // javascript

access per key

dic[key] # python
dic[key] // javascript

get iterarable / list

dic.keys() # python  iterable
Object.keys(dic) // javascript list

iteration

for key, value in dic.items(): # python
    <code>
for (const [key, value] of Object.entries(dict)) { // javascript
    <code>
}
Object.entries(dict).forEach( // javascript
    ([key, value]) => {
        <code>
    }
)

remove key-value

dic.pop("key") # python
dic.delete["key"] // javascript

check for key

'key-name' in dict # python
dict.hasOwnProperty('key-name') // javascript

catch unexisting key

try: # python
    value = dict[key]
except KeyError:
    <code>

let value = dict[key] // javascript
if (value == undefined) { <code> }

from string

dic = json.loads(st) # python
let dic = JSON.parse(st) // javascript

Deepcopy

a = copy.deepcopy(b) # python
a = structuredClone(b) // javascript

Traceback

import traceback # python
traceback.print_stack()
console.trace() // javascript

Subclassing

call superclass ctor

class ChildClass(ParentClass): # python
    def __init__(self):
        super()

class ChildClass extends ParentClass { // javascript
    constructor() { super() } // javascript

call superclass method

class SubClass(BaseClass): # python
    ...
    def someMethod():
        super().someMethod()

class SubClass extends BaseClass { // javascript
    ...
    someMethod() {
        super.someMethod(); // NOTE: no `()` in super
    }
}

Object Instance Members

self.member = 1 # python
this.member = 1 // javascript

Lambda Functions

f = lambda x: x+1 # python
(x) => { return x+1 } // javascript
x => x+1 // javascript

JS Scope

let x=1 // only withint current {} scope
const x=1 // only withint current {} scope
var x=1 // { var x=1 {seen also in this scope} }