histogram.py

Source code

################################
# Program No 0
# simple program for histogram
#  - without functions
#  - prompting user for the input
#
#################################
# Build a histogram
from collections import defaultdict
counters = defaultdict(int)
input_list = []
entries = int(input("Number of entries? "))
for _ in range(entries):
  userval = int(input("Enter value:"))
  input_list.append(userval)
  counters[userval] += 1

if input_list:
  print("Input values", input_list)
  histogram = sorted(counters.items())
  print("Histogram", histogram)
  print("Visualize the histogram")
  for i in range(len(histogram)):
    print (f'{histogram[i][0]:2}', '*'*histogram[i][1])
else:
  print("No values available to build histogram")

################################
# Program No 1
# using dictionary to build the histogram
#   - using a randomizer for input
#   - functionally decomposing the logic
#
#################################
# Build a histogram

import random
# build a random list
# returns a list containing numbers 1 <= v <= maxval
# the list will contain n elements where
#   mincount < n < maxcount
def random_list(mincount, maxcount, maxval, minval=1):
  size = random.randint(mincount, maxcount)
  alist = []
  for _ in range(size):
    alist.append(random.randrange(minval, maxval+1))
  return alist

arlist = random_list(50, 120, 20, -10)
print("A random list", arlist)


# returns a list containig tuples with
# value and frequency, aka a histogram
from collections import defaultdict
def generate_histogram(arlist):
  counters = defaultdict(int) #inits value to 0
  for number in arlist:
	  counters[number] += 1

  histogram = sorted(counters.items())
  return histogram

histo = generate_histogram(arlist)
print("A histogram with", histo)

print("Visualizing the histogram")
for i in range(len(histo)):
  print (f'{histo[i][0]:2}', '*'*histo[i][1])


################################
# Program No 2
# without using dictionary
#
#################################

# returns a list of tuples with value and frequency
def generate_histogram2(arlist):
  counters = [0] * (1+max(arlist)) # non-zero values

  for number in arlist:
    try:
      counters[number] += 1
    except:
      print(f'**** Error with {number}!')
      print(f'--- in {histo} with {len(histo)}')

  histogram = [(i,n)
	  for i, n in enumerate(counters) if n
	]
  return histogram

arlist = random_list(50, 120, 20) # positive integers
print("A random list", arlist)

histo = generate_histogram2(arlist)
print("A histogram with", histo)

print("Visualizing the histogram")
for i in range(len(histo)):
  print (f'{histo[i][0]:2}', '*'*histo[i][1])

Assignment

1. How many distinct programs are there in the above code?

2. What is the main advantage of Program 1 over Program 2?

3. What is the main advantage of Program 2 over Program 1?

4. Modify Program 1 to display an ordered histogram.

Misc

1. Provide commentary on the below program source code

2. Is it okay to use this code for teaching?

3. If not, why not?

###########################
#
# from Charulatha PDF
#
###########################
def histogram(items):
  for n in items:
    output = ''
	times = n
	while(times > 0):
	  output += '@'
	  times = times - 1
	  print(output)

histogram([2, 3, 6, 5])

1. Write a program that prints a histogram of frequencies of alphabet characters occurring in a message.