Possible code improvement suggestion: Use `is not None` rather than bool() for None check

[skasturi]

Code Sample, a copy-pastable example if possible

While going through the code I observed at couple of places where bool(o) is being used to check whether the object o is None.

Example 1:

pandas/pandas/core/strings.py

Line 449 in 6620dc6

f = lambda x: bool(regex.search(x))

Example 2:

pandas/pandas/core/strings.py

Line 821 in 6620dc6

f = lambda x: bool(regex.match(x))

Problem description

bool(o) is several times slower than o is not None (see below). In the above cases however, majority of the time indeed is being taken by the re.search and therefore it might not matter for the overall time. But, why not switch to the possibly correct version?

Moreover, the functionality remains the same as re.search and re.match return None when they cannot find a match; which is fundamentally what is being checked in this code.

[skasturi]

... and I will be sending out a PR to fix this.