2. Variable Assignments

>>> a=7
>>> a
7
>>> a=a+a
>>> a
14
>>> a=a/7
>>> a
2.0
>>> a=a-2
>>> a
0.0

The names you use when creating these labels need to follow a few rules:

1. Names can not start with a number.
2. There can be no spaces in the name, use _ instead.
3. Can't use any of these symbols :'",<>/?|\()!@#$%^&*~-+
4. It's considered best practice that names are lowercase.
5. Avoid using the characters 'l' (lowercase letter el), 'O' (uppercase letter oh),
or 'I' (uppercase letter eye) as single character variable names.
6. Avoid using words that have special meaning in Python like "list" and "str"

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3. Determining variable type with type()

>> a=7
>>> type(a)
<class 'int'>

>>> b=7.7
>>> type(b)
<class 'float'>

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

>>> d=[1,2,3]
>>> type(d)
<class 'list'>

>>> e=(1,2,3)
>>> type(e)
<class 'tuple'>

>>> f={1:"one",2:"two"}
>>> type(f)
<class 'dict'>

>>> g={1,2,3}
>>> type(g)
<class 'set'>

>>> i=True
>>> type(i)
<class 'bool'>





You can check what type of object is assigned to a variable using Python's built-in type() function. Common data types include:

int (for integer)
float
str (for string)
list
tuple
dict (for dictionary)
set
bool (for Boolean True/False)

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4. String Basics

>>> s='python_codes'
>>> s
'python_codes'

>>> len(s)
12

>>> s[0]
'p'

>>> s[1:]
'ython_codes'

>>> s
'python_codes'

>>> s[:7]
'python_'

>>> s[:]
'python_codes'

>>> s[::1]
'python_codes'

>>> s[::-1]
'sedoc_nohtyp'

>>> var = "a"
>>> var*10
'aaaaaaaaaa'

>>> s=s+" python channel"
>>> s
'python_codes python channel'

>>> s.upper()
'PYTHON_CODES PYTHON CHANNEL'

>>> s.lower()
'python_codes python channel'

>>> s.split('codes')
['python_', ' python channel']

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5. Lists

>>> list=[8,0,5,1]
>>> list
[8, 0, 5, 1]

>>> len(list)
4

>>> list_2=['string',8086,'p']
>>> list_2
['string', 8086, 'p']

>>> len(list_2)
3

Indexing and Slicing

>>> list=['one','ox','ok']
>>> list[0]
'one'

>>> list[1:]
['ox', 'ok']

>>> list[:2]
['one', 'ox']

>>> list[-1]
'ok'

>>> list[::-1]
['ok', 'ox', 'one']

>>> list+[235]
['one', 'ox', 'ok', 235]

>>> list*2
['one', 'ox', 'ok', 'one', 'ox', 'ok']

Basic List Methods

>>> list=[4,0,1,3]
>>> list.append("new")
>>> list
[4, 0, 1, 3, 'new']

>>> list.pop(0)
4
>>> list
[0, 1, 3, 'new']

>>> list.reverse()
>>> list
['new', 3, 1, 0]


Nesting Lists

>>> lst_1=[1,2,3]
>>> lst_2=[4,5,6]
>>> lst_3=[7,8,9]
>>> matrix = [lst_1,lst_2,lst_3]
>>> matrix
[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

>>> matrix[1]
[4, 5, 6]

>>> matrix[0][1]
2

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6. Conditionals

example

x = 5

if x == 5:
print("x equals 5")
else:
print("x does not equal 5")

it will output

x equals 5

🍏 other operators

x = 6
if x > 5:
print("x greater than 5")
else:
print("x less than 5")

outputs

x greater than 5

other operators

< less than
!= not equal to
>= greater equal to
<= less equal to

smart python

if 3<x<5:

means if x between 3 and 5

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# ASCII
p=ord("A")
q=ord('a')
print(p,q)

output: 65 97

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