Simple Cheet sheet by Shijo Shaji
Commenting
Printing to Terminal
Arithmetic Operators
Variables
BooleanÂ
Logical Operators
If Conditionals
While Loops
Array/List
For Loops
Functions
Strings
Object / Dictionaries
TBD
TBD
TBD
TBD
# PRESENTING CODE
if (x == 2) {
console.log("x must be 2")
} else {
if (x == 3) {
console.log("x must be 3")
} else {
console.log("x must be something else")
}
}Whitespace is Javascript has no meaning. Blocks of code are declared with braces { }. Indentation is used for readability.
if x == 2:
print("x must be 2")
else:
if x == 3:
print("x must be 3")
else:
print("x must be something else")# PRESENTING CODE
You can use space or tab. Without proper indentation, you will get an error
// Single Line Comment# PRESENTING CODE
/*
* Multiple line:
* Anything between here is a
comment- this
can extend several lines*/# Single Line Comment# PRESENTING CODE
"""
Multiple Line comment
At this pointanything between triple quotes are comments
"""// JAVASCRIPT
console.log("print this!")# PRESENTING CODE
# PYTHON
print("print this to terminal")// JS Variables declaration
let x = "Hello there"
const y = "Good bye"# PRESENTING CODE
# Python variables declaration
x = "Hello there"
y = "Good bye"Arithmetic Operators
The arithmetic operators between Javascript and Python are identical — except for one.
Python is missing:
pre-decrement/ post-decrement,
pre-increment/ post-increment operators.
since Python treats all numbers as floats (decimal numbers), you can use the double division sign // to get an integer.
// Javascript users lowercase
let x = true;
let y = false;# PRESENTING CODE
# Python users Uppercase
x = True;
y = False;// Javascript
=== Strict equality
!== Strict inequality
// Example:
0 == "0" // true
0 === "0" // false
0 == [] // true
0 === [] // false
0 == 0 // true
0 === 0 // true# PRESENTING CODE
The boolean operators between Javascript and Python are identical — except for two extra JS operators. Python is missing the strict equality/inequality operators.
// Javascript
! //Logical inverse, not
&& //Logical AND
|| //Logical OR# PRESENTING CODE
# Python
not # Logical inverse, not
and # Logical AND
or # Logical OR// Javascript
if (x == 10) {
console.log("x is 10")
} else if (x == 20) {
console.log("x is 20")
} else {
console.log("x is something else")
}# PRESENTING CODE
# Python
if x == 10:
print("x is 10")
elif x == 20:
print("x is 20")
else:
print("x is something else")// Javascript
let x = 10
while (x >= 0) {
console.log(x)
x--
}
// output: 10 down to 0# PRESENTING CODE
# Python
x = 10
while x >= 0:
print(x)
x -= 1
# prints from 10 down to 0// Javascript
for (let i = 0; i < 10; i++) {
console.log(i)
}
// Output : 0-9# PRESENTING CODE
# Python
for i in range(10):
print(i)
# Prints 0-9
# we can iterate over types
a = [10, 20, 30]
for i in a:
print(i) # Print 10 20 30
# dictionary
b = {'x':5, 'y':15, 'z':0}
for i in b:
print(i) # Print x y z (the keys of the dict)// Javascript Creating Array
let a1 = new Array() // Empty array
let a2 = new Array(10) // Array of 10 elements
let a3 = [] // Empty array
let a4 = [10, 20, 30] // Array of 3 elements
let a5 = [1, 2, "b"] // No problem# PRESENTING CODE
In JS, they are called arrays.
In Python, they are called lists.
# Python creating List
a1 = list() # Empty list
a2 = list((88, 99)) # List of two elements
a3 = [] # Empty list
a4 = [10, 20, 30] # List of 3 elements
a5 = [1, 2, "b"] # No problem// Javascript Accessing Array
console.log(a4[1]) // prints 20
a4[0] = 5 // change from 10 to 5
a4[20] = 99 // OK, makes a new element at index 20
a4.length; // 3# PRESENTING CODE
In JS, they are called arrays.
In Python, they are called lists.
# Python Accessing List
print(a4[1]) # prints 20
a4[0] = 5; # change from 10 to 5
a4[20] = 99; # ERROR: assignment out of range
len(a4) # 3// Javascript Add/Remove Array
const fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi") // adds Kiwi to list
fruits.pop("Kiwi") // removes Kiwi from list# PRESENTING CODE
In JS, they are called arrays.
In Python, they are called lists.
# Python Add/Remove List
fruits = ["Banana", "Orange", "Apple", "Mango"]
fruits.append("Kiwi") # adds Kiwi to list
fruits.remove("Kiwi") # removes Kiwi from list// Javascript Add with index Array
const fruits = ["Banana", "Apple", "Mango"];
fruits.splice(1, 0, "orange") // will insert the value "orange" as the second element of the fruit# PRESENTING CODE
In JS, they are called arrays.
In Python, they are called lists.
# Python Add with index List
fruits = ["Banana", "Apple", "Mango"]
fruits.insert(1, "orange") # will insert the value orange as the second element of the fruit list// Javascript Add with index Array
const fruits = ["Banana", "Apple", "Mango"];
fruits.pop()
// will remove and return the last element from the list # PRESENTING CODE
In JS, they are called arrays.
In Python, they are called lists.
# Python remove with index List
fruits = ["Banana", "Apple", "Mango", "Grape"]
fruits.pop()
# will remove and return the last element from the list
fruits.pop(2)
# will remove and return the element with index 2 from the list// Javascript
const fruits= ["Banana", "Orange", "Lemon", "Apple", "Mango"]
const slicedFruits = letters.slice(1, 3)
console.log(slicedFruits) // ["Orange", "Lemon"]# PRESENTING CODE
"""
In Python, we perform slicing using the following syntax: [start: end].
start is the index of the first element that we want to include in our selection.
end is the index of one more than the last index that we want to include.
"""
fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"]
sliced_fruits = fruits[1:3]
print(sliced_fruits) # ["Orange", "Lemon"]# PRESENTING CODE
"""
Slicing in Python is very flexible.
If we want to select the first n elements of a list or the last n elements in a list,
we could use the following code:
fruits[:n]
fruits[-n:]
"""
fruits = ["Banana", "Orange", "Lemon", "Apple", "Mango"]
# For our fruits list, suppose we wanted to slice the first three elements.
print(fruits[:3]) # ["Banana", "Orange", "Lemon"]
print(fruits[-2:]) # ["Apple", "Mango"]
# We can also do all but n last elements of a list:
print(fruits[:-1]) # ["Banana", "Orange", "Lemon", "Apple"]
# PRESENTING CODE
// Javascript
const names = ["Xander", "Buffy", "Angel", "Willow", "Giles"]
names.sort()
console.log(names) // ['Angel', 'Buffy', 'Giles', 'Willow', 'Xander']"""
Python : .sort() / .sorted()
.sort() Sort modifies the list directly.
.sorted() generates a new list instead of modifying one that already exists and sorts
"""
names = ["Xander", "Buffy", "Angel", "Willow", "Giles"]
names.sort()
print(names) # ['Angel', 'Buffy', 'Giles', 'Willow', 'Xander']
# Reverse List and sort
names.sort(reverse=True)
print(names) # ['Xander', 'Willow', 'Giles', 'Buffy', 'Angel']
# sorted()
sorted_names = sorted(names)
print(sorted_names) # ['Angel', 'Buffy', 'Giles', 'Willow', 'Xander']// Javascript
function foobar(x, y, z) {
console.log(x, y, z)
return 12
}
// Arrow Function
let hello = () => {
console.log("hello")
console.log("world")
}
// prints hello, then world# PRESENTING CODE
# Python
def foobar(x, y, z):
print(x, y, z)
return 12
// Javascript .toUpperCase() / toLowerCase()
let str = "Hello World!"
str.toUpperCase() // HELLO WORLD!
str.toLowerCase() // hello world!# PRESENTING CODE
# Python .upper() / .lower()
str = "Hello World!"
str.upper() # HELLO WORLD!
str.lower() # hello world!Strings in Python and Javascript both use single and double-quotes
// Javascript
let food1 = {} // empty object
let food2 = {pizza: "tomato"} // property quotes optional
// common multiline format
let prices= {
"pizza": 20,
"pasta": 1.2,
"drink": "free"
}
console.log(prices.pizza) // prints 20
console.log(prices["drink"]) // prints free# PRESENTING CODE
# Python
food1 = {} # empty dict
food2 = {"pizza": "tomato"} # key quotes are required
# multiline format
prices = {
"pizza": 20,
"pasta": 1.2,
"drink": "free"
}
print(prices["pizza"]) # Prints 20In Javascript, objects hold data that can be found using a key called a property.
In Python, these key/value pairs are called dictionaries.