Simplify String Length Comparison

Sourcery refactoring id: simplify-string-len-comparison

Description:

Changes an indirect comparison of a string's length to 0 into a direct comparison of the string to the empty string.

Before:

if len(s) == 0:
    ...

if len(r) > 0:
    ...

After:

if s == "":
    ...

if r != "":
    ...

Explanation:

This refactoring avoids an unnecessary calculation and keeps the logic in the domain of string types. It tends to unlock further improvements to string comparisons.