Use pass for an empty block

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms in 
#Python by Madhavan Mukund, Chennai Mathematical Institute 

while(True):  
  try:
    userdata = input("Enter a number: ")
    usernum = int(userdata)
  except ValueError:
    print("Not a number. Try again")
  except NameError:
    pass
  else:
    break  

Check wheather a number is composite or not

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms in 
#Python by Madhavan Mukund, Chennai Mathematical Institute 
 
def composite(n):
      for i in range(2,n):
        if n%i == 0:
          return(True)
      return(False)

Divison with multiple conditions

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms in 
#Python by Madhavan Mukund, Chennai Mathematical Institute 


def divides(m,n):
  if n%m == 0:
    return(True)
  else:
    return(False)


def even(n):
  return(divides(2,n))


def odd(n):
  return(not divides(2,n))

GCD using euclids algorithms & looping

# Credits to NPTEL MOOC,Programming, Data Structures & Algorithms 
#in Python by Madhavan Mukund, Chennai Mathematical Institute

def gcd(m,n):
  if m < n:  # Assume m >= n
    (m,n) = (n,m)
  while (m%n) != 0:
    diff = m-n
    # diff > n? Possible!
    (m,n) = (max(n,diff),min(n,diff))
  return(n)

Greatest common divisor program using euclids algorithms

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms in 
#Python by Madhavan Mukund, Chennai Mathematical Institute 
 
def gcd(m,n):
    if m < n:
        (m,n) = (n,m)
    if (m%n) == 0:
        return(n)
    else:
        diff = m-n
        return(gcd(max(n,diff),min(n,diff)))

print(gcd(12,3))

Greatest common divisor program with looping

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms in 
#Python by Madhavan Mukund, Chennai Mathematical Institute 


def gcd(m,n):
  i = min(m,n)
  while i > 0:
    if (m%i) == 0 and (n%i) == 0:
      return(i)
    else:
      i = i-1

Greatest common divisor program without list Implementation

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms in 
#Python by Madhavan Mukund, Chennai Mathematical Institute 

def gcd(m,n):
  for i in range(1,min(m,n)+1):
    if (m%i) == 0 and (n%i) == 0:
      mrcf = i
  return(mrcf)

Greatest common divisor program - A shorter Implementation

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms #in Python by Madhavan Mukund, Chennai Mathematical Institute

def gcd(m,n):
  cf = []
  for i in range(1,min(m,n)+1):
    if (m%i) == 0 and (n%i) == 0:
      cf.append(i)
  return(cf[-1])

Greatest common divisor program

#Credits to NPTEL MOOC, Programming, Data Structures & Algorithms in 
#Python by Madhavan Mukund, Chennai Mathematical Institute 

def gcd(m,n):
  fm = []
  for i in range(1,m+1):
    if (m%i) == 0:
      fm.append(i)
  fn = []
  for j in range(1,n+1):
    if (n%j) == 0:
      fn.append(j)
  cf = []
  for f in fm:
    if f in fn:
      cf.append(f)
  return(cf[-1])

Calculation of Gross and Net Calorific Value

#  Credits   Name: ANUPRIYA R

#  HCV - Higher and Gross Calorific Value
#  LCV -  Lower or Net Calorific Value
# Compatible with python 3.x.x

c=float(input("enter value of carbon in %: "))
h=float(input("enter value of hydrogen in %: "))
s=float(input("enter value of sulphur in %: "))
o=float(input("enter value of oxygen in %: "))
HCV=(8080*c+34500*(h-o/8)+2240*s)*1/100
LCV=(HCV-0.09*h*587)
print ("Higher calorific value of sample is ",HCV)
print("Lower calorific value of sample is ",LCV)