How do I take the first value and the last value from a list with a list in python?

Question

from operator import itemgetter
file = open("testdata.txt","r")
filein = []
for row in file:
       filein.append(row.strip("\n"))
results= []
for item in filein:
    results.append(item.split(","))
counter=0
for item in results:
    itemlength = len(item)
    for i in range(1, itemlength):
        item[i] = int(item[i])
        item.append(max(results[counter][1:4]))
        item.append((sum(results[counter][1:4]))/3)
        counter=counter+1
results.sort()
print("\n")
print(sorted(results,key=itemgetter(5),reverse=True))

[['DF', 8, 6, 8, 8, 7.333333333333333], ['ED', 10, 4, 6, 10, 6.666666666666667], ['TH', 9, 4, 7, 9, 6.666666666666667], ['EK', 9, 4, 5, 9, 6.0]]

I have two questions. The first one is how can I print the first value (initials) with the 5th value [4], which is the highest score, in a new list? My second question how can I get the average score[5] of the three scores to 2 decimal places?

This task is for my assessment, I hope that you could help me out! Thank you

Padraic Cunningham · Answer 1 · 2015-03-25T21:32:54.817

2

You can unpack and use str.format, {:.2f} will format the average to two decimal places:

l = [['DF', 8, 6, 8, 8, 7.333333333333333], ['ED', 10, 4, 6, 10, 6.666666666666667],
     ['TH', 9, 4, 7, 9, 6.666666666666667], ['EK', 9, 4, 5, 9, 6.0]]

for ini, _, _, _, highest, avg in l:
    print("Initials: {}, highest : {}, average: {:.2f}".format(ini, highest, avg))

Initials: DF, highest : 8, average: 7.33
Initials: ED, highest : 10, average: 6.67
Initials: TH, highest : 9, average: 6.67
Initials: EK, highest : 9, average: 6.00

edited Mar 25 '15 at 21:32

answered Mar 25 '15 at 20:53

Padraic Cunningham

176,452
29
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2

`_` as variable name. and it i s working. great +upvote – Vivek Sable Mar 25 '15 at 20:56
1

@VivekSable the `_`, just signifies that we are not going to use the values. – Padraic Cunningham Mar 25 '15 at 20:57
which is best format method? `"{}, {}, {:.2f}".format(i[0], i[4], i[5])` OR ` "%s, %d, %.2f"%(i[0], i[4], i[5])` – Vivek Sable Mar 25 '15 at 21:09
1

@VivekSable, I prefer `str.format`, it is less error prone and more readable to me anyway. As far as python goes `str.format` would also be the preferred method. http://stackoverflow.com/questions/5082452/python-string-formatting-vs-format – Padraic Cunningham Mar 25 '15 at 21:13
Thank you so much @Padraic Cunningham – Mar 25 '15 at 21:26
@VivekSable,no worries. – Padraic Cunningham Mar 25 '15 at 21:31

Vivek Sable · Answer 2 · 2015-03-25T21:06:55.440

Round decimal number:

Demo:

>>> round(1.7777, 2)
1.78
>>> round(1.7777, 0)
2.0
>>>

>>> "%.2f"%(1.239)
'1.23'

Use subscription to get value from th list.

Demo

>>> l = ["a", "b", "c", "d"]  
>>> l[0]   #- First item
'a'
>>> l[-1]   #- Last item
'd'
>>> l[3]     #- Last item i.e. Item from the index 3  
'd'
>>>

code:

>>> l = [['DF', 8, 6, 8, 8, 7.333333333333333], ['ED', 10, 4, 6, 10, 6.666666666666667], ['TH', 9, 4, 7, 9, 6.666666666666667], ['EK', 9, 4, 5, 9, 6.0]]
>>> for i in l:...    print "%s, %d, %.2f"%(i[0], i[4], i[5])
... 
DF, 8, 7.33
ED, 10, 6.67
TH, 9, 6.67
EK, 9, 6.00
>>>

score 0 · Answer 3 · answered Mar 25 '15 at 20:52

0

Just keep subscripting.

>>> mylist = [[1,2],[5,6]]
>>> mylist[0]
[1,2]
>>> mylist[0][1]
2

answered Mar 25 '15 at 20:52

TigerhawkT3

48,464
6
60
97

score 0 · Answer 4 · answered Mar 25 '15 at 20:53

To get 1st and last elements in a new list

l = [['DF', 8, 6, 8, 8, 7.333333333333333], ['ED', 10, 4, 6, 10, 6.666666666666667], ['TH', 9, 4, 7, 9, 6.666666666666667], ['EK', 9, 4, 5, 9, 6.0]]
l2 = []
for i in l:
    l2.append([i[0], i[-1]])

print l2

l2 = [['DF', 7.333333333333333], ['ED', 6.666666666666667], ['TH', 6.666666666666667], ['EK', 6.0]]

How do I take the first value and the last value from a list with a list in python?

4 Answers4