Honestly, I don’t really care if you struggle with syntax. I’m making you a simple cheatsheet while this does not have everything it has the essesstials.

Print it. Pin it on the wall. Bookmark this page. Keep this handy.

Variables

<name of variable> = <value>

pi = 3.14
name = "Harsh Deep"
age = 18

Types

Integers

These are just whole numbers. Positive, negative and zero. Ex. 3, 4, 0, -4234, 523542354

To convert:

>>> int("42")
42

Pretty reliable to do math on. Careful though, division only returns the whole number part.

Floats

Same as integers, but can have decimal parts. Ex. 13423.4234, 0.0, -42.0

To convert:

>>> float("2.718")
2.718

You can do most math on these, but careful because computers are weird with rounding.

Strings

These are how programs represent strings. You can’t do math on Ex. "", "Harsh Deep", '42'

To convert:

>>> str(42)
'42'
>>> str(1000.5)
'1000.5'

For length:

>>> len("Harsh")
5

Math

>>> 1 + 3
4
>>> 2.0 - 0.5
1.5
>>> 1.5 * 9
13.5
>>> 18/4   # Float division
4.5 
>>> 18//4  # Integer division
4
>>> 5**2 # 5^2 or 5 to the power of 2
25

Other math is pretty similar.

Blocks

How python marks a chunk of code, useful for the next sections.

block_start:
    line1
    line2
    line3

So it’s started with a :, then every line is indented one level (4 spaces). To mark the end of the block leave an empty line or start another block.

Nested blocks

block_start1:
    line1
    line2
    block_start2:
        line3
        line4

    line5

If conditions

For branching

if grade > 90:
    print("A")
elif grade > 80:
    print("B")
else:
    print("C")

Boolean logic

Inequalities. Either output True or False

>>> 5 == 5
True
>>> 5 > 4
True
>>> 5 < 4
False
>>> 5 >= 5
True
>>> 4 <= 2
False

Combining:

# And gives true only when both are true
>>> True and True
True
>>> True and False
False

# Or gives true when atleast one is true
>>> False or False 
False
>>> False or True
True
>>> True or True # Both being true is still true
True

# Not just flips in
>>> not True
False
>>> not False
True

Loops

While

Simple looping

while(condition):
    what_ever_you_wanna_loop

The loop stops when the condition becomes false. It’s basically like a loop version of an if condition.

while(not_good_at_programming && i_want_to_learn_to_get_better):
    practice()
    learn()
    ask()
    teach()
    create()

For

Looping over something or a certain number of times.

Ranges - a range of numbers

for i in range(10):
    print(i)

Ranges with a start and end

for teen in range(13, 19):
    print(teen)

For strings

for letter in "Harsh Deep":
    print(letter)

Lists

Python3 has LinkedList, or array with no fixed length like data structure for storing many elements.

Delcare

Empty

empty_list = []

Non empty

primes = [1, 2, 3, 5, 7, 11, 13, 17, 19, 21, 23, 29]

Read

>>> squares = [1, 4, 9, 16, 25]
>>> squares[0] # First element
1
>>> squares[1] # Second element
4
>>> squares[4] # Last element
25
>>> squares[-1] # Better way to get last element
25
>>> squares[-2] # Second last element
16

Write

>>> squares = [1, 4, 9, 16, 25]
>>> squares[2] = 36 # Just use an equals to change whatever
>>> squares
[1, 4, 36, 16, 25]

Append

You can add to the end of the list.

>>> squares = [1, 4, 9, 16, 25]
>>> squares.append(36)
>>> squares
[1, 4, 9, 16, 25, 36]

Pop

Remove the last element of the list.

>>> squares
[1, 4, 9, 16, 25, 36]
>>> squares.pop()
36
>>> squares
[1, 4, 9, 16, 25]

Insert

>>> numbers = [1, 2, 4, 5]
>>> numbers.insert(2, 3) # Oops forgot to add 3, let's add 3 at position 2
>>> numbers
[1, 2, 3, 4, 5]

Functions

The python (and lots of other languages) way of named blocks of code.

>>> def add(number1, number2):
...     return number1 + number2
... 
>>> print(add(1, 3))
4

note the empty line. Return is how we show the output of our function.

Execution stops when we hit return.

No parameters

>>> def father_of_cs():
...     return "Alan Turing"
...
>>> father_of_cs()
'Alan Turing'

No return

>>> def hi():
...     print("Hi how are you doing")
...
>>> hi()
Hi how are you doing

Basically if you don’t need to return something just don’t include it.

Other cheatsheets

And the best: the one you make for yourself. I highly highly suggest you do one for yourself. It won’t have the parts you don’t care and only the stuff you want to remember.