Formatting data in a CSV file (calculating average) in python - csv

Question

import csv
with open('Class1scores.csv') as inf:
for line in inf:
parts = line.split()
if len(parts) > 1:
print (parts[4])
f = open('Class1scores.csv')
csv_f = csv.reader(f)
newlist = []
for row in csv_f:
row[1] = int(row[1])
row[2] = int(row[2])
row[3] = int(row[3])
maximum = max(row[1:3])
row.append(maximum)
average = round(sum(row[1:3])/3)
row.append(average)
newlist.append(row[0:4])
averageScore = [[x[3], x[0]] for x in newlist]
print('\nStudents Average Scores From Highest to Lowest\n')
Here the code is meant to read the CSV file and in the first three rows (row 0 being the users name) it should add all the three scores and divide by three but it doesn't calculate a proper average, it just takes the score from the last column.

Answer 1

Basically you want statistics of each row. In general you should do something like this:
import csv
with open('data.csv', 'r') as f:
rows = csv.reader(f)
for row in rows:
name = row[0]
scores = row[1:]
# calculate statistics of scores
attributes = {
'NAME': name,
'MAX' : max(scores),
'MIN' : min(scores),
'AVE' : 1.0 * sum(scores) / len(scores)
}
output_mesg ="name: {NAME:s} \t high: {MAX:d} \t low: {MIN:d} \t ave: {AVE:f}"
print(output_mesg.format(**attributes))
Try not to consider if doing specific things is inefficient locally. A good Pythonic script should be as readable as possible to every one.
In your code, I spot two mistakes:
Appending to row won't change anything, since row is a local variable in for loop and will get garbage collected.
row[1:3] only gives the second and the third element. row[1:4] gives what you want, as well as row[1:]. Indexing in Python normally is end-exclusive.
And some questions for you to think about:
If I can open the file in Excel and it's not that big, why not just do it in Excel? Can I make use of all the tools I have to get work done as soon as possible with least effort? Can I get done with this task in 30 seconds?

Answer 2

Here is one way to do it. See both parts. First, we create a dictionary with names as the key and a list of results as values.
import csv
fileLineList = []
averageScoreDict = {}
with open('Class1scores.csv', newline='') as csvfile:
reader = csv.reader(csvfile)
for row in reader:
fileLineList.append(row)
for row in fileLineList:
highest = 0
lowest = 0
total = 0
average = 0
for column in row:
if column.isdigit():
column = int(column)
if column > highest:
highest = column
if column < lowest or lowest == 0:
lowest = column
total += column
average = total / 3
averageScoreDict[row[0]] = [highest, lowest, round(average)]
print(averageScoreDict)
Output:
{'Milky': [7, 4, 5], 'Billy': [6, 5, 6], 'Adam': [5, 2, 4], 'John': [10, 7, 9]}
Now that we have our dictionary, we can create your desired final output by sorting the list. See this updated code:
import csv
from operator import itemgetter
fileLineList = []
averageScoreDict = {} # Creating an empty dictionary here.
with open('Class1scores.csv', newline='') as csvfile:
reader = csv.reader(csvfile)
for row in reader:
fileLineList.append(row)
for row in fileLineList:
highest = 0
lowest = 0
total = 0
average = 0
for column in row:
if column.isdigit():
column = int(column)
if column > highest:
highest = column
if column < lowest or lowest == 0:
lowest = column
total += column
average = total / 3
# Here is where we put the emtpy dictinary created earlier to good use.
# We assign the key, in this case the contents of the first column of
# the CSV, to the list of values.
# For the first line of the file, the Key would be 'John'.
# We are assigning a list to John which is 3 integers:
# highest, lowest and average (which is a float we round)
averageScoreDict[row[0]] = [highest, lowest, round(average)]
averageScoreList = []
# Here we "unpack" the dictionary we have created and create a list of Keys.
# which are the names and single value we want, in this case the average.
for key, value in averageScoreDict.items():
averageScoreList.append([key, value[2]])
# Sorting the list using the value instead of the name.
averageScoreList.sort(key=itemgetter(1), reverse=True)
print('\nStudents Average Scores From Highest to Lowest\n')
print(averageScoreList)
Output:
Students Average Scores From Highest to Lowest
[['John', 9], ['Billy', 6], ['Milky', 5], ['Adam', 4]]