Colon (:) in Python list index
Question:
I’m new to Python. I see : used in list indices especially when it’s associated with function calls.
Python 2.7 documentation suggests that lists.append translates to a[len(a):] = [x]. Why does one need to suffix len(a) with a colon?
I understand that : is used to identify keys in dictionary.
Answers:
: is the delimiter of the slice syntax to ‘slice out’ sub-parts in sequences , [start:end]
[1:5] is equivalent to "from 1 to 5" (5 not included)
[1:] is equivalent to "1 to end"
[len(a):] is equivalent to "from length of a to end"
Watch https://youtu.be/tKTZoB2Vjuk?t=41m40s at around 40:00 he starts explaining that.
Works with tuples and strings, too.
slicing operator. http://docs.python.org/tutorial/introduction.html#strings and scroll down a bit
a[len(a):] – This gets you the length of a to the end. It selects a range. If you reverse a[:len(a)] it will get you the beginning to whatever is len(a).
I’m new to Python. I see : used in list indices especially when it’s associated with function calls.
Python 2.7 documentation suggests that lists.append translates to a[len(a):] = [x]. Why does one need to suffix len(a) with a colon?
I understand that : is used to identify keys in dictionary.
: is the delimiter of the slice syntax to ‘slice out’ sub-parts in sequences , [start:end]
[1:5] is equivalent to "from 1 to 5" (5 not included)
[1:] is equivalent to "1 to end"
[len(a):] is equivalent to "from length of a to end"
Watch https://youtu.be/tKTZoB2Vjuk?t=41m40s at around 40:00 he starts explaining that.
Works with tuples and strings, too.
slicing operator. http://docs.python.org/tutorial/introduction.html#strings and scroll down a bit
a[len(a):] – This gets you the length of a to the end. It selects a range. If you reverse a[:len(a)] it will get you the beginning to whatever is len(a).