Python Advanced

1 Python Advanced

Python methods:

# Instance method

# function vs method

class Class1:

    def func():

        print('hi')

print(type (Class1.func))  # access funtion directly from class (function)

object = Class1()

print(type (object.func)) ##function becomes a method when called via object/instance

# of a class.

# Classmethod

class Person:

    def __init__(self, first_name, last_name, age):

        self.first_name = first_name

        self.last_name = last_name

        self.age = age

    def full_name(self):

        return f"{self.first_name} {self.last_name}"

    @classmethod    

    def other(cls):

        return Person('John', 'Cena', 25)

obj1 = Person.other()

print(obj1.full_name())

#

# Static method

class multiplier:

   

    # static method are used for grouping similar functions

    # or uitility methods under a class

    @staticmethod

    def mutli_by_2(c):

        return 2*c + 100

           

    @staticmethod

    def mutli_by_5(f):

        return 5*f + 100

m = multiplier.mutli_by_2(25)

print(m)

m1 = multiplier.mutli_by_5(50)

print(m1)

Higher order functions:

# Higher order functions

def sum1(x):

    return x + 1

def sum2(func, x):

    result = func(x)

    return result

print(sum2(sum1,5))

O/p:

6

Closure:

If a variable goes out of scope or if function is removed from the current namespace. Even then if variable is remembered then this concept is called Clossure. 

Closusre requirements:

1- Nested function

2- Nested function refer value from Outer function(enclosing function)

3- Outer function should return nested function

# Outer enclosing function

def sum1(a):

   

    # Nested function

    def sum2():

        print(a)

    return sum2  # Returning Nested function

int1 = sum1(5)

int1()

O/p:

5

Decorators:

A function which takes another function as an argument and extends its behavior without changing the original function is called a Decorator. (add functionality to an existing code).

from functools import wraps

class decorator:

    def __init__(self, n):

        self.n = n

    def __call__(self, fn):

        @wraps(fn)

        def wrapper(*args, **kwargs):

            print(self.n*'*')

            result = fn(*args, **kwargs)

            print(result)

            print(self.n*'*')

            return result

        return wrapper

@decorator(10)

def sum(a, b, c):

    return a + b + c

sum(5, 6, 4)

O/p:

**********

15

**********

Python Generators:

# Generator function

n = 0

def my_gen():

    global n

    n += 1

    print('Printed first')

    yield n

    n += 1

    print('Printed 2nd')

    yield n

for item in my_gen():

    print(item)

O/p:

Printed first

1

Printed 2nd

2

2 SQL Server DB Connection

1) start the services in management studio

SQL server configuration manger start services

2) start the sql server

3) create DB, query

CREATE TABLE EMPLOYEE (

         NAME  CHAR(20) NOT NULL,

         AGE INT,  

         INCOME FLOAT );

insert into EMPLOYEE values ('emp1', 31, 90000.00);

select * from EMPLOYEE;

Step 1: Install pyodbc

(base) C:\Users\user1>pip install pyodbc

Step2: Retrieve the server name

Server name: User\User1SQL

Step 3: Obtain the database name

Database name: sql_db

Step 4: Get the table name

Table name: dbo.EMPLOYEE

Connect Python IDE to SQL Server:

import pyodbc 

conn = pyodbc.connect('Driver={SQL Server};'

                      'Server=User1\User1SQL;'

                      'Database=sql_db;'

                      'Trusted_Connection=yes;')

cursor = conn.cursor()

cursor.execute('SELECT * FROM sql_db.dbo.EMPLOYEE')

for row in cursor:

    print(row)

##Insert values to SQL server Table from Python:

import pyodbc 

conn = pyodbc.connect('Driver={SQL Server};'

                      'Server=User1\User1SQL;'

                      'Database=sql_db;'

                      'Trusted_Connection=yes;')

cursor = conn.cursor()

cursor.execute('SELECT * FROM sql_db.dbo.EMPLOYEE1')

cursor.execute('''

                INSERT INTO sql_db.dbo.EMPLOYEE1 (NAME, AGE, INCOME)

                VALUES

                ('Bob',55,85000),

                ('Jenny',66,86000)

                ''')

conn.commit()

Loading data from SQL Server to Python pandas dataframe
import pandas as pd
import pyodbc

conn = pyodbc.connect('Driver={SQL Server};'
                      'Server=User1\User1SQL;'
                      'Database=sql_db;'
                      'Trusted_Connection=yes;')
#query = "SELECT [BusinessEntityID],[FirstName],[LastName],
 #                [PostalCode],[City] FROM [Sales].[vSalesPerson]"

query = "SELECT * FROM sql_db.dbo.EMPLOYEE1"
df = pd.read_sql(query, conn)


df.head(3)

3 Random password Generation

import random

# Function to shuffle characters of a string
def shuffle(string):
  tempList = list(string)  # string to list
  random.shuffle(tempList) # Random shuffling list
  return ''.join(tempList) # join the random shffled templist to String

char1_uppercase=chr(random.randint(65,90))
char2_lowercase=chr(random.randint(97,122))
char3_special  =chr(random.randint(35,38))
char4_lowercase=chr(random.randint(97,122))
char5_lowercase=chr(random.randint(97,122))
char6_lowercase=chr(random.randint(97,122))
char7_lowercase=chr(random.randint(97,122))
char8_lowercase=chr(random.randint(97,122))

password = char1_uppercase + char2_lowercase + char3_special +\

           char4_lowercase + char5_lowercase + char6_lowercase  + \

           char7_lowercase + char8_lowercase 

password = shuffle(password)
print("password is :", password)

password is : fkmTh#bm