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How do I sort the second column of this Python output in descending fashion?

I can't seem to get this code to sort on avg_n_ratings in descending fashion.
Can someone please advise on how to do so, thanks.
genres_ios = freq_table(ios_final, -5)
for genre in genres_ios:
total = 0
len_genre = 0
for app in ios_final:
genre_app = app[-5]
if genre_app == genre:
n_ratings = float(app[5])
total += n_ratings
len_genre += 1
avg_n_ratings = total / len_genre
print(genre, ':', avg_n_ratings)
Here are the unsorted results to the code as is.

At the moment you just print your statements one by one, no sorting possible. You need to bunch them together (e.g. to a list) to get a sorting done.
Try this:
genres_ios = freq_table(ios_final, -5)
result = []
for genre in genres_ios:
total = 0
len_genre = 0
for app in ios_final:
genre_app = app[-5]
if genre_app == genre:
n_ratings = float(app[5])
total += n_ratings
len_genre += 1
avg_n_ratings = total / len_genre
result.append((genre, avg_n_ratings))
sorted_list = sorted(result, key= lambda tup: tup[1])
# the key makes the list be sorted by the 2nd element (which is the number) of each tuple
print(sorted_list)

Need to find top 10 used surnames in a files. Made a dictonary but need to sort it the rest

I made a surname dict containing surnames like this:
--The files contains 200 000 words, and this is a sample on the surname_dict--
['KRISTIANSEN', 'OLDERVIK', 'GJERSTAD', 'VESTLY SKIVIK', 'NYMANN', 'ØSTBY', 'LINNERUD', 'REMLO', 'SKARSHAUG', 'ELI', 'ADOLFSEN']
I am not allow to use counter library or numpy, just native Python.
My idea was to use for-loop sorting through the dictionary, but just hit some walls. Please help with some advice.
Thanks.
surname_dict = []
count = 0
for index in data_list:
if index["lastname"] not in surname_dict:
count = count + 1
surname_dict.append(index["lastname"])
for k, v in sorted(surname_dict.items(), key=lambda item: item[1]):
if count < 10: # Print only the top 10 surnames
print(k)
count += 1
else:
break

As mentioned in a comment, your dict is actually a list.
Try using the Counter object from the collections library. In the below example, I have edited your list so that it contains a few duplicates.
from collections import Counter
surnames = ['KRISTIANSEN', 'OLDERVIK', 'GJERSTAD', 'VESTLY SKIVIK', 'NYMANN', 'ØSTBY', 'LINNERUD', 'REMLO', 'SKARSHAUG', 'ELI', 'ADOLFSEN', 'OLDERVIK', 'ØSTBY', 'ØSTBY']
counter = Counter(surnames)
for name in counter.most_common(3):
print(name)
The result becomes:
('ØSTBY', 3)
('OLDERVIK', 2)
('KRISTIANSEN', 1)
Change the integer argument to most_common to 10 for your use case.

The best approach to answer your question is to consider the top ten categories :
for example : category of names that are used 9 times and category of names that are used 200 times and so . Because , we could have a case where 100 of users use different usernames but all of them have to be on the top 10 used username. So to implement my approach here is the script :
def counter(file : list):
L = set(file)
i = 0
M = {}
for j in L :
for k in file :
if j == k:
i+=1
M.update({i : j})
i = 0
D = list(M.keys())
D.sort()
F = {}
if len(D)>= 10:
K = D[0:10]
for i in K:
F.update({i:D[i]})
return F
else :
return M
Note: my script calculate the top ten categories .

You could place all the values in a dictionary where the value is the number of times it appears in the dataset, and filter through your newly created dictionary and push any result that has a value count > 10 to your final array.
edit: your surname_dict was initialized as an array, not a dictionary.
surname_dict = {}
top_ten = []
for index in data_list:
if index['lastname'] not in surname_dict.keys():
surname_dict[index['lastname']] = 1
else:
surname_dict[index['lastname']] += 1
for k, v in sorted(surname_dict.items()):
if v >= 10:
top_ten.append(k)
return top_ten

Just use a standard dictionary. I've added some duplicates to your data, and am using a threshold value to grab any names with more than 2 occurences. Use threshold = 10 for your actual code.
names = ['KRISTIANSEN', 'OLDERVIK', 'GJERSTAD', 'VESTLY SKIVIK', 'NYMANN', 'ØSTBY','ØSTBY','ØSTBY','REMLO', 'LINNERUD', 'REMLO', 'SKARSHAUG', 'ELI', 'ADOLFSEN']
# you need 10 in your code, but I've only added a few dups to your sample data
threshold = 2
di = {}
for name in names:
#grab name count, initialize to zero first time
count = di.get(name, 0)
di[name] = count + 1
#basic filtering, no sorting
unsorted = {name:count for name, count in di.items() if count >= threshold}
print(f"{unsorted=}")
#sorting by frequency: filter out the ones you don't want
bigenough = [(count, name) for name, count in di.items() if count >= threshold]
tops = sorted(bigenough, reverse=True)
print(f"{tops=}")
#or as another dict
tops_dict = {name:count for count, name in tops}
print(f"{tops_dict=}")
Output:
unsorted={'ØSTBY': 3, 'REMLO': 2}
tops=[(3, 'ØSTBY'), (2, 'REMLO')]
tops_dict={'ØSTBY': 3, 'REMLO': 2}

Update.
Wanted to share what code I made in the end. Thank you guys so much. The feedback really helped.
Code:
etternavn_dict = {}
for index in data_list:
if index['etternavn'] not in etternavn_dict.keys():
etternavn_dict[index['etternavn']] = 1
else:
etternavn_dict[index['etternavn']] += 1
print("\nTopp 10 etternavn:")
count = 0
for k, v in sorted(etternavn_dict.items(), key=lambda item: item[1]):
if count < 10:
print(k)
count += 1
else:
break

Python File IO - building dictionary and finding max value

Problem is to return the name of the event that has the highest number of participants in this text file:
#Beyond the Imposter Syndrome
32 students
4 faculty
10 industries
#Diversifying Computing Panel
15 students
20 faculty
#Movie Night
52 students
So I figured I had to split it into a dictionary with the keys as the event names and the values as the sum of the integers at the beginning of the other lines. I'm having a lot of trouble and I think I'm making it too complicated than it is.
This is what I have so far:
def most_attended(fname):
'''(str: filename, )'''
d = {}
f = open(fname)
lines = f.read().split(' \n')
print lines
indexes = []
count = 0
for i in range(len(lines)):
if lines[i].startswith('#'):
event = lines[i].strip('#').strip()
if event not in d:
d[event] = []
print d
indexes.append(i)
print indexes
if not lines[i].startswith('#') and indexes !=0:
num = lines[i].strip().split()[0]
print num
if num not in d[len(d)-1]:
d[len(d)-1] += [num]
print d
f.close()

import sys
from collections import defaultdict
from operator import itemgetter
def load_data(file_name):
events = defaultdict(int)
current_event = None
for line in open(file_name):
if line.startswith('#'):
current_event = line[1:].strip()
else:
participants_count = int(line.split()[0])
events[current_event] += participants_count
return events
if __name__ == '__main__':
if len(sys.argv) < 2:
print('Usage:\n\t{} <file>\n'.format(sys.argv[0]))
else:
events = load_data(sys.argv[1])
print('{}: {}'.format(*max(events.items(), key=itemgetter(1))))

Here's how I would do it.
with open("test.txt", "r") as f:
docText = f.read()
eventsList = []
#start at one because we don't want what's before the first #
for item in docText.split("#")[1:]:
individualLines = item.split("\n")
#get the sum by finding everything after the name, name is the first line here
sumPeople = 0
#we don't want the title
for line in individualLines[1:]:
if not line == "":
sumPeople += int(line.split(" ")[0]) #add everything before the first space to the sum
#add to the list a tuple with (eventname, numpeopleatevent)
eventsList.append((individualLines[0], sumPeople))
#get the item in the list with the max number of people
print(max(eventsList, key=lambda x: x[1]))
Essentially you first want to split up the document by #, ignoring the first item because that's always going to be empty. Now you have a list of events. Now for each event you have to go through, and for every additional line in that event (except the first) you have to add that lines value to the sum. Then you create a list of tuples like (eventname) (numPeopleAtEvent). Finally you use max() to get the item with the maximum number of people.
This code prints ('Movie Night', 104) obviously you can format it to however you like

Similar answers to the ones above.
result = {} # store the results
current_key = None # placeholder to hold the current_key
for line in lines:
# find what event we are currently stripping data for
# if this line doesnt start with '#', we can assume that its going to be info for the last seen event
if line.startswith("#"):
current_key = line[1:]
result[current_key] = 0
elif current_key:
# pull the number out of the string
number = [int(s) for s in line.split() if s.isdigit()]
# make sure we actually got a number in the line
if len(number) > 0:
result[current_key] = result[current_key] + number[0]
print(max(result, key=lambda x: x[1]))
This will print "Movie Night".

Your problem description says that you want to find the event with highest number of participants. I tried a solution which does not use list or dictionary.
Ps: I am new to Python.
bigEventName = ""
participants = 0
curEventName = ""
curEventParticipants = 0
# Use RegEx to split the file by lines
itr = re.finditer("^([#\w+].*)$", lines, flags = re.MULTILINE)
for m in itr:
if m.group(1).startswith("#"):
# Whenever a new group is encountered, check if the previous sum of
# participants is more than the recent event. If so, save the results.
if curEventParticipants > participants:
participants = curEventParticipants
bigEventName = curEventName
# Reset the current event name and sum as 0
curEventName = m.group(1)[1:]
curEventParticipants = 0
elif re.match("(\d+) .*", m.group(1)):
# If it is line which starts with number, extract the number and sum it
curEventParticipants += int(re.search("(\d+) .*", m.group(1)).group(1))
# This nasty code is needed to take care of the last event
bigEventName = curEventName if curEventParticipants > participants else bigEventName
# Here is the answer
print("Event: ", bigEventName)

You can do it without a dictionary and maybe make it a little simpler if just using lists:
with open('myfile.txt', 'r') as f:
lines = f.readlines()
lines = [l.strip() for l in lines if l[0] != '#'] # remove comment lines and '\n'
highest = 0
event = ""
for l in lines:
l = l.split()
if int(l[0]) > highest:
highest = int(l[0])
event = l[1]
print (event)

Sort Average In A file

I have a file with 3 scores for each person. Each person has their own row. I want to use these scores, and get the average of all 3 of them. There scores are separated by tabs and in descending order. For example:
tam 10 6 11
tom 3 7 3
tim 5 4 6
these people would come out with an average of:
tam 9
tom 5
tim 4
I want these to be able to print to the python shell, however not be saved to the file.
with open("file.txt") as file1:
d = {}
count = 0
for line in file1:
column = line.split()
names = column[0]
average = (int(column[1].strip()) + int(column[2].strip()) + int(column[3].strip()))/3
count = 0
while count < 3:
d.setdefault(names, []).append(average)
count = count + 1
for names, v in sorted(d.items()):
averages = (sum(v)/3)
print(names,average)
averageslist=[]
averageslist.append(averages)
My code only finds the first persons average and outputs it for all of them. I also want it to be descending in order of averages.

You can use the following code that parses your file into a list of (name, average) tuples and prints every entry of the by average sorted list:
import operator
with open("file.txt") as f:
data = []
for line in f:
parts = line.split()
name = parts[0]
vals = parts[1:]
avg = sum(int(x) for x in vals)/len(vals)
data.append((name, avg))
for person in sorted(data, key=operator.itemgetter(1), reverse=True):
print("{} {}".format(*person))

You are almost correct.You are calculating average in the first step.So need of sum(v)/3 again.Try this
with open("file.txt") as file1:
d = {}
count = 0
for line in file1:
column = line.split()
names = column[0]
average = (int(column[1].strip()) + int(column[2].strip()) + int(column[3].strip()))/3
d[names] = average
for names, v in sorted(d.items(),key=lambda x:x[1],reverse=True): #increasing order==>sorted(d.items(),key=lambda x:x[1])
print(names,v)
#output
('tam', 9)
('tim', 5)
('tom', 4)
To sort by name
for names, v in sorted(d.items()):
print(names,v)
#output
('tam', 9)
('tim', 5)
('tom', 4)

The issue is this:
averages = (sum(v)/3)
print(names,average)
Notice that on the first line you are computing averages (with an s at the end) and on the next line you are printing average (without an s).

Try This:
from operator import itemgetter
with open("file.txt") as file1:
d = {}
count = 0
for line in file1:
column = line.split()
names = column[0]
average = (int(column[1].strip()) + int(column[2].strip()) + int(column[3].strip()))/3
count = 0
d.setdefault(names, []).append(average)
for names,v in sorted(d.items(), key=itemgetter(1),reverse=True):
print(names,v)

Finding Maximum Value in CSV File

Have an assignment of finding average and maximum rainfall in file "BoulderWeatherData.csv". Have found the average using this code:
rain = open("BoulderWeatherData.csv", "r")
data = rain.readline()
print(rain)
data = rain.readlines()
total = 0
linecounter = 0
for rain in data:
linecounter = linecounter + 1
print("The number of lines is", linecounter)
for line in data:
r = line.split(",")
total = total + float(r[4])
print(total)
average = float(total / linecounter)
print("The average rainfall is ", "%.2f" % average)
However, can't seem to find maximum using this same process. Attempted using max, function but the answer that must be obtained is float number, which can not be iterated through max.
Any help would be appreciated.

This is my prefered way of handling this.
#!/usr/bin/env python3
rain = open("BoulderWeatherData.csv","r")
average = 0.0
total = 0
maxt = 0.0
for line in rain:
try:
p = float(line.split(",")[4])
average += p
total += 1
maxt = max(maxt,p)
except:
pass
average = average / float(total)
print("Average:",average)
print("Maximum:",maxt)
This will output:
Average: 0.05465272591486193
Maximum: 1.98

import csv
INPUT = "BoulderWeatherData.csv"
PRECIP = 4 # 5th column
with open(INPUT, "rU") as inf:
incsv = csv.reader(inf)
header = next(incsv, None) # skip header row
precip = [float(row[PRECIP]) for row in incsv]
avg_precip = sum(precip, 0.) / (1 and len(precip)) # prevent div-by-0
max_precip = max(precip)
print(
"Avg precip: {:0.3f} in/day, max precip: {:0.3f} in/day"
.format(avg_precip, max_precip)
)
returns
Avg precip: 0.055 in/day, max precip: 1.980 in/day

max=0
for line in data:
r = line.split(",")
if float(r[4]) > max:
max=float(r[4])
print(max)
something like that

You're already accumulating total across loop iterations.
To keep track of a maxvalue, it's basically the same thing, except instead of adding you're maxing:
total = 0
maxvalue = 0
for line in data:
r = line.split(",")
value = float(r[4])
total = total + value
maxvalue = max(maxvalue, value)
print(total)
print(maxvalue)
Or, if you don't want to use the max function:
for line in data:
r = line.split(",")
value = float(r[4])
total = total + value
if value > maxvalue:
maxvalue = value

This code will attempt to find the maximum value, and the average value, of floats stored in the 5th position in a .csv.
rainval = []
Initializes the empty array where we will store values.
with open ("BoulderWeatherData.csv", "r") as rain:
Opens the .csv file and names it "rain".
for lines in rain:
This reads every line in rain until the end of the file.
rainval += [float(lines.strip().split(",")[4])]
We append the float value found in the fifth position (fourth index) of the line.
We repeat the above for every line located in the .csv file.
print (sorted(rainval)[len(rainval)])
This sorts the values in the rainval array and then takes the last (greatest) value, and prints it. This is the maximum value and is better than max because it can handle floats and not just ints.
print (sum(rainval)/len(rainval))
This prints the average rainfall.
Alternatively, if we don't want to use arrays:
maxrain = -float("inf")
total, count = 0, 0
with open ("test.txt", "r") as rain:
for lines in rain:
temp = float(lines.strip().split(",")[4])
if maxrain < temp:
maxrain = temp
total += temp
count += 1
print (maxrain)
print (total/count)