ref - Python

import my_math.arith.ops
import my_math.arith.ops.PI
from math import sqrt as sq
print(sq(25))

a= my_math.arith.ops.add(3,5);

#Function
def add(n1, n2):
    return n1+n2;

a = add(4,5);
print(a)

def fnc(x, y, z = None):
    x = x * x
    y = y * y
    if z == None:
        z = []
    return x, y, z

x, y, z = fnc(10, 20, "arfin")
print(x,y,z)

#Split, Join, rjust, ljust, center, format
lis = ['a', 'b', 'c']
joined = ','.join(lis)
print(joined)

li = joined.split(',')
print(li)

s = "abc"
li = list(s)
s = '+'.join(li)
print(s)

for i in range(15):
    print(str(i).rjust(2))

s = '1000'.rjust(10)
print(s)
s = '1000'.center(10)
print(s)
s = '12'.zfill(6)
print(s)

print("{0} vs {1}".format("BN", "IN"))
print("{team1} vs {team2}".format(team1 = "BN", team2 = "IN"))

#FILE I/O
file = 'text.txt'
fp = open(file, 'w')
fp.write("this is us")
fp.close();
fp = open(file, 'a')
fp.write("this is appended")
fp.close()
fp = open(file, 'r')
fp.read()
fp.close()
fp = open(file, 'r')
fp.radline();
fp.seek(0)
fp.readline()
fp.seek(1)
fp.readline()
fp.seek(0)
for line in fp:
    print(line)
fp.close()

with open(file, 'r') as fp:
    data = fp.read()
    print(data)

#Error & exception handling

def div(a,b):
    try:
        result = a/b
    except ZeroDivisionError:
        print("Division by 0 is not possible")
    except TypeError:
        print("Data type not supported")
    else:
        return result
    finally:
        print("inside finally")

print(div(4,2))
div(4,0)
div('4', 2)

for i in range(10):
    print(i)
else:
    print("Inside Else")




#OOP in python

#Declare
class Square:
    side = 0;
    def __init__(self, x):
        self.side = x
    def area(self):
        return self.side * self.side;

sq = Square(4);
area = sq.area();
print(area)

#Inheirtance

class Rect:
    x = 0;
    y = 0;
    def __init__(self):
        print("Inside rect")
    def area(self, x, y):
        return self.x * self.y

class Sq(Rect):
    def __init__(self):
        print("Inside sq")

sq = Sq()
print(sq.area(4,4))

print(sq.__class__)

print(isinstance(sq, Sq))
print(isinstance(sq, Rect))
print(isinstance(sq, Square))

print(issubclass(Sq,Sq))
print(issubclass(Sq, Rect))
print(issubclass(Sq, Square))


#Iterator
li = [1,2,3]
print(li.__iter__)

city = 'Dhaka'
print(city.__iter__)

icity = iter('Dhaka')
print(next(icity))
print(next(icity))
print(next(icity))
#Doesnt works for some reason :/
class Reverse:
    """Iterator for looping over a sequence backwards."""
    def __init__(self, data):
        self.data = data
        self.index = len(data)
    def __iter__(self):
        return self
    def next(self):
        if self.index == 0:
            raise StopIteration
        self.index = self.index - 1
        return self.data[self.index]

rev = Reverse("abcd")
print(rev)
next(rev)


#Generators
def reverse(data):
    for index in range(len(data)-1, -1, -1):
        yield data[index]

for ch in reverse('abcd'):
    print(ch)

gen = reverse('defh')
print(type(gen))

for char in gen:
    print(char)

for char in gen:
    print(char)

def gen(n):
    i = 0
    while i < n:
        yield i
        i = i + 1
x = gen(5)
print(x)

for item in x:
    print(item)