Python

Applications & Webpages

• Python IDLE
• Pycharm
• Intellij Idea

• https://peps.python.org/pep-0008/
• https://automatetheboringstuff.com/2e/
• https://www.w3schools.com/python/default.asp

Basic Syntax

# Leave a comment by prepending a "#" to your command

# Print "Hello World"
>>> print("Hello World!")
Hello World!

# Echo 3 strings
>>> "Hello" + " " + "World"
'Hello World'

# Add a newline to a value
>>> print("Hello World!\n")
Hello World!


# Escape an escape character
>>> print("Hello World\\n")
Hello World\n

# Single apostrophe is usable inside double-quotes
>>> "Hello 'orld"
"Hello 'orld"

# Escape a double apostrophe
>>> "Hello \"World"
'Hello "World'

Value types

# Find out the type of a value
>>> type (1 + 2)
<class 'int'>

>>> type (4 / 2)
<class 'float'>

>>> type("hello")
<class 'str'>

>>> type(False)
<class 'bool'>

>>> mytuple = ("pizza", "pancake")
>>> type(mytuple)
<class 'tuple'>

# Set a value as a specific value-type
>>> int(4.0)
4
>>> float(2)
2.0

Basic math

# Add values together
>>> 2 + 3
5

# Two to the power of 3
>>> 2 ** 3
8

# Divide whole numbers
>>> 9 / 2
4.5

# Divide whole number but print the number on the left side of the comma
>>> 9 // 2
4

# Modulo - The remainder after subtracting 2 as many times as you can
>>> 9 % 2
1

# Display the lowest or highest value of a set values
>>> min(5, 1, 8)
1

>>> max(5, 1, 8)
8

Variables

# Define a variable
>>> a = 3

# Display the contents of a variable
>>> a = 3
>>> a
3

# Swap the contents of 2 variables
>>>  b, c = c, b

# Create a list
>>> d = [5, "Bami", 3]

# Fetch the second entry from a list
>>> d[1]
'Bami'

# Modify the value of a list entry
>>> d[2]
3
>>> d[2] = 7
>>> d[2]
7


# Create a Tuple (immutable list)
>>> e = (5, "Bami", 3)

# Fetch the second entry of a Tuple
>>> e[1]
'Bami'


# Display a specific character of a variable
>>> s = "Apple"
>>> s[0]
'A'

>>> s[-1]
'e'

Operators

Comparison

<=     = Smaller than or equal
>=     = Bigger than or equal
<      = Smaller than
>      = Bigger than 
==     = Equal
!=     = Is not equal

and    = Is True if 2 given values is True
or     = Is True if either of 2 given values is True
not    = Turns False into True, or True into False

Boolean

# True and False
>>> True - False
1

>>> False
False

>>> False + False
0

>>> int(False)
0

>>> int(False) + int(True)
1

# Comparisons
>>> 2 < 3
True

>>> 2 > 3
False

>>> 2 == 3
False

>>> 2 != 3
True

Common blocks

if

# If block and expression
if ( n % 2 == 1 ):
    print("Weird")

# if and elif blocks with expressions
if ( n % 2 == 1 ):
    print("Weird")
elif ( n >= 3 and n <= 5 and n % 2 == 0):
    print("Not Weird")

for

# Basic for loop printing each character separately
for char in name:
    print(char)

# For loop that checks for "top" inside words and lists the words
for word in ('stop', 'desktop', 'post', 'top'):
    if 'top' in word:
         print(word)
print('Done.')

# Output list entries using a for loop
names = ["Alex", "Alice", "Baba", "Bertha"]
a_list = [name for name in names if name[0] == "A"]
print(a_list)

range

# Print digits 0 through 3 using the range function
for number in range(3):
    print(number)
    

# Print digits 0 through 3 but don't output on a newline
for number in range(3):
    print(number, end=" ")
    
# Print digit for every 2 numbers between 0 and 11, starting from 0
for number in range(0, 11, 2):
    print(number, end=" ")

try

# The following takes 2 user-inputs, adds their values together and outputs it and prints that the block is finished.
try:
    INPUTONE = int(input())
    INPUTTWO = int(input())
except ValueError:
    print("Invalid input. Please enter an integer.")
else:
    print(INPUTONE + INPUTTWO)
finally:
  print("Finished")

function

# Define a basic function, printing a message
 def greeting():
       print('Hello mortal')

greeting()

# Define a function using a variable input
name = input("What is your name?")

def hello(var):
    print('Hello ' + var)

hello(name)

# Same as above but prettier and more chaotic
def hello(var):
    greeting = "Hello " + var
    return greeting

print(str(hello(input("What is your name?"))))

Basics

If you're going to work with pip packages on Linux, always create a venv.

# Create a venv in folder .venv/
python3 -m venv .venv/

# Activate your virtual environment
source .venv/bin/activate

# You can list active pip packages with pip list
pip list

# Deactivate your virtual environment
deactivate