*www.codingdojo.com (on indeed.com listings)

Python is a popular choice for beginners, yet still powerful enough to to back some of the world’s most popular products and applications from companies like NASA, Google, Mozilla, Cisco, Microsoft, and Instagram, among others.

Python’s design makes the programming experience feel almost as natural as writing in English

Python Cheat Sheet

Math Operators

From Highest to Lowest precedence:

**            >>>   Exponent                    >>>  2 ** 3 = 8
%             >>>   Modulus/Remainder           >>>  22 % 8 = 6
//            >>>   Integer division            >>>  22 // 8 = 2
/             >>>   Division                    >>>  22 / 8 = 2.75
*             >>>   Multiplication              >>>  3 * 3 = 9
-             >>>   Subtraction                 >>>  5 - 2 = 3
+             >>>   ADITTION                    >>>  22 + 8 = 30

## Examples of expressions in the interactive shell:
 
>>> 2 + 3 * 6 
20
>>> (2 + 3) * 6 
30
>>> 23 % 7 
2
>>> (5 - 1) * ((7 + 1) / (3 - 1)) 
16.0
>>> 3-3
0
>>> 3/3
1
>>> 3*3
9
>>> 3**3
27

String Concatenation and Replication

String concatenation:

>> 'Alice' 'Bob' 
'AliceBob'

String Replication:

>>> 'Alice' * 5
'AliceAliceAliceAliceAlice'

Variables

You can name a variable anything as long as it obeys the following rules:

1. It can be only one word.
2. It can use only letters, numbers, and the underscore (_) character.
3. It can’t begin with a number.

>>> spam = ‘Hello’
>>> spam
‘Hello’

The print() Function

>>> print('Hello world!')
Hello world!

The input() Function

>>> print('What is your name?')   # ask for their name
>>> myName = input()
>>> print('It is good to meet you, {}'.format(myName))
What is your name?
Al
It is good to meet you, Al

The len() Function

Evaluates to the integer value of the number of characters in a string:

>>> len('hello')
5

Note: test of emptiness of strings, lists, dictionary, etc, should not use len, but prefer direct boolean evaluation.

>>> a = [1, 2, 3] 
>>> if a: 
>>> print("the list is not empty!")

The str(), int(), and float() Functions

integer to String or Float

>>> str(29)
'29'
>>> print('I am {} years old.'.format(str(29)))
I am 29 years old.
>>> str(-3.14)
'-3.14'

Float to Integer:

>>> int(7.7)
7
>>> int(7.7) + 1
8

Flow Control

Comparison Operators

>>> 42 == 42
True
>>> 40 == 42
False
>>> 'hello' == 'hello'
True
>>> 'hello' == 'Hello'
False
>>> 'dog' != 'cat'   #not equal to
True
>>> 42 == 42.0
True
>>> 42 == '42'
False

Boolean evaluation

Use the is or is not operators, or use implicit boolean evaluation.

>>> True is True
True
>>> True is not False
True
###These statements are equivalent:
>>> if a is True:
>>>    pass
>>> if a is not False:
>>>    pass
>>> if a:
>>>    pass

Boolean Operators
There are three Boolean operators: and, or, and not.

Mixing Boolean and Comparison Operators

>>> (4 < 5) and (5 < 6)
True
>>> (4 < 5) and (9 < 6)
False
>>> (1 == 2) or (2 == 2)
True
##You can also use multiple Boolean operators in an expression, along with the comparison operators:
>>> 2 + 2 == 4 and not 2 + 2 == 5 and 2 * 2 == 2 + 2 
True

if Statements

if name == 'Alice':     
   print('Hi, Alice.')

else Statements

name = 'Bob'
if name == 'Alice':
    print('Hi, Alice.')
else:
    print('Hello, stranger.')

elif Statements

name = 'Bob'
age = 5
if name == 'Alice':
    print('Hi, Alice.')
elif age < 12:
    print('You are not Alice, kiddo.')
name = 'Bob'
age = 30
if name == 'Alice':
    print('Hi, Alice.')
elif age < 12:
    print('You are not Alice, kiddo.')
else:
    print('You are neither Alice nor a little kid.')

while Loop Statements

spam = 0
while spam < 5:
    print('Hello, world.')
    spam = spam + 1

break Statements

If the execution reaches a break statement, it immediately exits the while loop’s clause:

while True:
    print('Please type your name.')
    name = input()
    if name == 'your name':
        break
print('Thank you!')

Taking break helps you understand yourself better.

End of part 1

Thank you

#Writingwhile studying.

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