py1. Creating combinations in Python

We can use combinations function from itertools module to create combinations:

#ex1a.py
from itertools import combinations

A = [1,2,3]

B = list(combinations(A,2))

print 'The list is ', B, ' with a length of ', len(B)

## The list is  [(1, 2), (1, 3), (2, 3)]  with a length of  3

We can also create a function using the factorials function

# ex1b.py
from math import factorial
def choose1(n,k):
    return factorial(n)/factorial(k)/factorial(n-k)
print choose1(n=3,k=2)
print choose1(3,2)
## 3
## 3