You already met some weak strings in the section about explicit evaluators. They are called weak because of two reasons:

• Explicit evaluators inside the string are indeed evaluated.
• When a weak string is explicitly evaluated, it loses the single quotes.

Example:

a = 2
b = 3
# Assign '5' to MyWeakString
MyWeakString = '(a+b)'
Print 'Result is (MyWeakString)'

Result is 5

Note that the result is 5, not '5', not (a+b) and not '(a+b)'.