I have a 2D list:
[['Hard', '7', '27.00'], ['David', '4', '26.00'], ['Great', '2', '25.00']]
I want to print it out in alphabetical order based on the first index of each list. I have a variable called listName which stores the information as presented above. I have tried listName.sort() however, it does not sort in alphabetical order. Any suggestions?
You have to pass a key argument to sort(). This function will sort the elements (in your case, each element is a list) based on the first item (x[0]) of that element:
listName.sort(key = lambda x:x[0])
Note: This will sort the lists based on an ASCII comparison (please, correct me if I'm wrong), therefore, it will put uppercase before lowercase. For example:
listName = [['Hard', '7', '27.00'], ['David', '4', '26.00'], ['Great', '2', '25.00'], ['a', '3', '123']]
listName.sort(key = lambda x:x[0])
print(listName)
# [['David', '4', '26.00'], ['Great', '2', '25.00'], ['Hard', '7', '27.00'], ['a', '3', '123']]
Two more options:
# The data
listName = [['Hard', '7', '27.00'], ['David', '4', '26.00'], ['Great', '2', '25.00'], ['a', '3', '123']]
# Use first element for sorting using operator.itemgetter (like x[0])
from operator import itemgetter
sorted(listName, key=itemgetter(0))
# Use a function instead of a lambda (+ case insensitive sorting)
def get(x):
# return first element of sublist and convert to lowercase
return x[0].lower()
sorted(listName, key=get)
Lambdas and function are very similar:
lambda x: x[0]
def get(x): return x[0]
The difference is that functions have a name and lambdas are anonymous (unless stored in a variable). You must not use return in a lambda, its behavior is always like there is one.
