How to use a for loop to loop through a nested list in Python

Question

I am currently trying to loop through and print specific values from a list. The way that I am trying to do this is like this.

for i in range(len(PrintedList)):
 index = i
 elem=PrintedList[i]
 print(elem)
 print ("Product = ", PrintedList [index,1], "price £",PrintedList [index,2])

However this returns the error of :

TypeError: list indices must be integers or slices, not tuple.

I am really unsure of what to do to fix the problem.

• salezica: Post the output (or a small sample) of print(PrintedList), so we can take a look at the actual structure. We can't guess by looking at code that doesn't work =)
• TidB: Is it possible you meant PrintledList[index][1] and PrintedList[index][2]?

Answer 1

Please do not iteerate using indeces, this is ugly and considered non-pythonic. Instead directly loop over list itself and use tuple-assignment, i.e.:

for product, price, *rest in PrintedList:
 print ("Product = ", product, "price £", price)

or

for elem in PrintedList:
 product, price, *rest = elem
 print ("Product = ", product, "price £", price)

*rest only required if some sublists contain more than 2 items (price and product)

if you need indeces, use enumerate:

for index, (product, price, *rest) in enumerate(PrintedList):
 print (index, "Product = ", product, "price £", price)

• SgtStens: Definitely the more pythonic way to do it, I was merely trying to address the specific error in the code. + 1 for the *rest, I didn't know about that.

Answer 2

When you're referencing a nested list, you reference each of the indices in separate brackets. Try this:

for i in range(len(PrintedList)):
 index = i
 elem=PrintedList[i]
 print(elem)
 print ("Product = ", PrintedList [index][1], "price £",PrintedList [index][2])