What are the key differences between using list() and ?
The most obvious and visible key difference between
 is the syntax. Putting the syntax aside for a minute here, someone whose new or intermediately exposed to python might argue that they’re both lists or derive from the same class; that is true. Which furthermore increases the importance of understanding the key differences of both, most of which are outlined below.
list() is a function and
 is literal syntax.
Let’s take a look at what happens when we call
respectively through the disassembler.
>>> import dis >>> print(dis.dis(lambda: list())) 1 0 LOAD_GLOBAL 0 (list) 3 CALL_FUNCTION 0 (0 positional, 0 keyword pair) 6 RETURN_VALUE None >>> print(dis.dis(lambda: )) 1 0 BUILD_LIST 0 3 RETURN_VALUE NoneThe output from the disassembler above shows that the literal syntax version doesn’t require a global lookup, denoted by the op code LOAD_GLOBAL or a function call, denoted by the op code CALL_FUNCTION. As a result, literal syntax is faster than it’s counterpart. – Let’s take a second and look at the timings below.
import timeit >>> timeit.timeit('', number=10**4) 0.0014592369552701712 >>> timeit.timeit('list()', number=10**4) 0.0033833282068371773On another note it’s equally important and worth pointing out that literal syntax,
does not unpack values. An example of unpacking is shown below.
>>> list('abc') # unpacks value ['a', 'b', 'c'] >>> ['abc'] # value remains packed ['abc']
Literals are notations or a way of writing constant or raw variable values which python recognises as built-in types.
It has been fun and interesting to write the first of many to come PythonRight blog posts; in the next blog post we’ll be going over the beauty of unpacking , so stay tuned. 😉 – If you have any feedback or any other topics that you’d like to see explained in detail, do feel free to comment.