Hello! I'm reading through, https://docs.python.org/3/tutorial/introduction.html#lists Please search for the following sentence: "This makes sure that s[:i] + s[i:] is always equal to s:" The meaning of a colon in the subscript has not been introduced yet. Thus not only does the above sentence not make sense to the reader, but the next example panel doesn't help. However, the material continuing from there does bring the reader back into alignment in understanding the text. Thanks, Kevin -- Kevin Low