A list is a mutable, ordered Python collection for storing, searching, extending, modifying, sorting, and replacing values. Use it naturally for sequences of related items, such as users, documents, or IP addresses. section 4.0
When working with a list, remember these practical distinctions:
- Retrieve an individual element with an index such as values[0] or values[-1]; retrieve a sub-list with a slice such as values[2:5]. section 4.3
- A single index can return any element type, while a list slice always returns another list; slices also tolerate boundaries beyond the list. section 4.3
- Build accumulated output with list.append and convert it afterward with str.join instead of repeatedly concatenating immutable strings. section 3.7
- Choose a list for a mutable sequence of related values; choose a tuple for an immutable record containing different kinds of values. section 4.0
- Use a comprehension when the purpose of the loop is to transform an iterable into a new list; use a for loop for side effects. section 8.2
Accumulate transformed characters
For a character-by-character transformation, create an empty output list, append either the transformed character or the original character, then join the completed list with ''. This prevents the loop from repeatedly rebuilding a string and avoids reprocessing newly inserted characters. section 3.11 section 3.7
Table 4.1 Sequence comparison
|
Type
|
Mutable?
|
Contains
|
Syntax
|
Retrieval
|
|---|---|---|---|---|
str
|
No
|
One-element strings
|
s = 'abc'
|
s[0] (Returns
'a')
|
list
|
Yes
|
Any Python type
|
mylist = [10, 20, 30, 40, 50]
|
mylist[2] (Returns
30)
|
tuple
|
No
|
Any Python type
|
t = (100, 200, 300, 400, 500)
|
t[3] (Returns
400)
|
Compare strings, lists, and tuples by mutability, contents, syntax, and indexed retrieval. section 4.0
