Retrieve data from the list on the basis of value in Python

April 8, 2022

In a Python program, I’m storing student information in a list, which I want to retrieve on the basis of value (class name).

Let’s say I want to print complete student details. I’ll write this code:

for i in range(len(studentDetails)):
    for j in range(len(studentDetails[i])):
        print(studentDetails[i][j], end=" ")
    print()

Data

studentDetail = [studentName, "Class: ", studentClass, "Marks:", studentMarks, "Grade: ", studentGrade]

[Dostoevsky, "Class: ", 1, "Marks: ", 100, "Grade: ", "A+"]
[Tolstoy, "Class: ", 1, "Marks: ", 90, "Grade: ", "A-"]
[Chekhov, "Class: ", 2, "Marks: ", 80, "Grade: ", "A"]
[Kafka, "Class: ", 2, "Marks: ", 75, "Grade: ", "B"]

I now want to print this way from the following data:

Result

Summary
Class 1
Dostoevsky    100    A+
Tolstoy        90    A-
Class 2
Chekhov       80     A
Kafka         75     B

>Solution :

Here is one way to do it:

studentDetails = [["Dostoevsky", "Class: ", 1, "Marks: ", 100, "Grade: ", "A+"],
["Tolstoy", "Class: ", 1, "Marks: ", 90, "Grade: ", "A-"],
["Chekov", "Class: ", 2, "Marks: ", 80, "Grade: ", "A"],
["Kafka", "Class: ", 2, "Marks: ", 75, "Grade: ", "B"]]
studentDetails.sort() #Sort the list by alphabetical order first
studentDetails.sort(key = lambda x: x[2]) #Sort the list by second element(classes)
print("Summary")
curClass = 0 #Current class nummber
for i in studentDetails: #Loops through all the student details
  if curClass != i[2]: #If the currect class number is not equal to the class number that's already printed
    curClass = i[2] #Replace the currect class number
    print("Class", curClass) #Print out the current class number
  print(i[0], i[4], i[6]) #Print out info

This works even when you add more data or class numbers. Hope it helps!