readnumbers2.py

######################################################################################
# Simple file read/math
#
# A simple example using file read, modulo, for loop, if/else, and "input sanitization."
# Basically reads in a comma separated list of values, and outputs count, sum, average,
# and number of evens and odds. Also notes the invalid inputs.
#
# Tested on a file with the following data:
# '100', '12', '22', '64', '2', '57', '99', '323', 'w', '6', '967', '3', '-2', '3.0', '5', '89', '32', '667', '3'
######################################################################################

# NOTE: A cleaner version of http://pastebin.com/kwtVP351

# Open the file into a file pointer
fp = open("numbers.txt","r")

# Use the file pointer to read the contents of the file into a string variable
text = fp.read()

# Close the file pointer
fp.close()

# Use the split() function to separate the comma-separated text file into a list
list = text.split(",")

# Output the list
print "This is the list:",list
print

# Initialize our statistics variables
average = 0

# Loop through the list of numbers and process each number
# Validate for whole numbers only
sanitizedList = [int(item) for item in list if item.isdigit()]
errorList = [item for item in list if not (item.isdigit())]

# Test for evens and odds using the modulo operation
# We will calculate the number of odds using subtraction
evensList = [item for item in sanitizedList if item % 2 ==0]

# Check for any errors
if len(errorList)>0:
    # Output an error message
    print "Non whole numbers detected:",errorList

# If there was more than one valid value, calculate the average using the sum and count variables
# Explicitly convert one value to float so that we get a more accurate average
# Without this, the value would be rounded to the nearest whole number.
listCount = len(sanitizedList)
if listCount>0:
  average = float(sum(sanitizedList))/listCount


#Output the results of the calculations
print
print "File Read Statistics"
print "--------------------"
print "Total number of whole numbers:",listCount
print "Sum of whole numbers:", sum(sanitizedList)
print "Average of whole numbers:", average
print "Total number of even whole numbers:", len(evensList)
print "Total number of odd whole numbers:", listCount - len(evensList)
print "Total number of input file errors:", len(errorList)
print
raw_input("Press Enter to exit")