Question

I am a new Python programmer and trying some stuff out. I want to create a list of strings and loop through my list to check the size of each element, if the size is greater than 5, then I will change that string into an uppercase string. I am stuck on how to access that element. Below is some of the code that I have written. Thank you in advance!

lis = ['heeeeellllooo','world','low','higggghhh']
for elem in list:
  if len(lis[elem]) > 5:
    list[elem].upper()

Answer 1

use a list comprehension with ternary operator:

In [16]: lis = ['heeeeellllooo','world','low','higggghhh']

In [17]: [x.upper() if len(x)>5 else x for x in lis] # this is a new list

Out[17]: ['HEEEEELLLLOOO', 'world', 'low', 'HIGGGGHHH']

You can also use enumerate(), enumerate returns a tuple whole first item is the index of the element and the second item is the element itself.

This method modifies the original list.

In [18]: for index,elem in enumerate(lis):
   ....:     if len(elem)>5:
   ....:         lis[index]=elem.upper()  #access element by index
   ....:         

In [19]: lis
Out[19]: ['HEEEEELLLLOOO', 'world', 'low', 'HIGGGGHHH']

How are lists implemented?:

Python’s lists are really variable-length arrays, not Lisp-style
linked lists. The implementation uses a contiguous array of references
to other objects, and keeps a pointer to this array and the array’s
length in a list head structure.

This makes indexing a list a[i] an operation whose cost is independent
of the size of the list or the value of the index.

When items are appended or inserted, the array of references is
resized. Some cleverness is applied to improve the performance of
appending items repeatedly; when the array must be grown, some extra
space is allocated so the next few times don’t require an actual
resize.