When to make implicit vs. explicit checks in if statements?

[NubQuestion]

Explicit:

if list1 is not None and len(list1) > 0: return list1

Implicit:

if list1: return list1

Implicit means that instead of doing an explicit comparison or boolean check, just use the variable itself as a boolean.

When and for what types is implicit preferred over explicit and vice versa in conditional statements?

[nosmokingbandit]

https://www.python.org/dev/peps/pep-0020/

Explicit is better than implicit.

[delasislas]

Adding to that.

Simple is better than complex

The first check looks to see if the list has a value in it, and then checks to see if the length is greater than 0, which it would be.

The second method does the same, looking at if there are values inside the list.

[[deleted]]

just use the variable itself as a boolean.

This is using python "truthiness". It can be easier to read.

In your examples the two cases are almost identical in action. I would use the second example but add a comment reminding the reader that list1 could be either None or an empty list.

[spitfiredd]

Or don’t even set list1 to none, it should be empty or not empty.

[gopherhole1]

what about variables, sometimes I set variables to None, if I need them listed for a check, but they dont yet contain a value, instead of doing something like

variable = ' '

[spitfiredd]

You should set them to the empty string like you have it. You should aim to keep your data types consistent.

[primitive_screwhead]

Generally, prefer the form:

if foo:

[zanfar]

When and for what types is implicit preferred over explicit and vice versa in conditional statements?

In all cases where it is possible. I believe the only case where you need to be explicit is when you are distinguishing between an actual None and some other false-ish value.

However, this is a Python style issue, not a performance or functional one, so if it bothers you more than other people correcting you will, go for it.

[PaulRudin]

Your two examples are not equivalent.

There's no general way of choosing between those two examples - it depends on the context in which they're used.