Adventures in Python:
Combinations and Permutations
This program offers the user a choice of one of three calculations:
1. Combinations, no
repeats
2. Permutations
3. Combinations, with
repeats
The program demonstrates how a menu is made. Equality is tested with two equal signs
(==). A single equal sign (=) represents
assignment for the Python.
The math.factorial function uses integers.
# Program 005: Combinations, Permutations,
Repeated Combination
# Demonstration of the If structure
import math
# factorial is only
for integers
# choices
# we will need to
format the choice variable as an integer (number)
print("Make
your choice:")
print("1. Combination")
print("2. Permutation")
print("3. Repeated Combination")
choice =
int(input("Choice: "))
# error condition,
also input routine
if choice < 1 or
choice > 3:
print("Not a valid choice")
else:
n = int(input("n = "))
r = int(input("r = "))
nf = math.factorial(n)
rf = math.factorial(r)
df = math.factorial(n-r)
# calculation
test. Equality is tested using 2 equal
signs
if choice == 1:
calc = nf/(df*rf)
print("Combinations = ",calc)
if choice == 2:
calc = nf/df
print("Permutations = ",calc)
if choice == 3:
calc =
math.factorial(n+r-1)/(rf*math.factorial(n-1))
print("Combinations = ",calc)
Example: n = 52, r = 5
Make your
choice:
1. Combination
2. Permutation
3. Repeated Combination
Choice: 1
n = 52
r = 5
Combinations
= 2598960.0
>>>
Make your
choice:
1. Combination
2. Permutation
3. Repeated Combination
Choice: 2
n = 52
r = 5
Permutations
= 311875200.0
>>>
Make your
choice:
1. Combination
2. Permutation
3. Repeated Combination
Choice: 3
n = 52
r = 5
Combinations
= 3819816.0
Eddie
This blog is property of Edward Shore, 2017.
