Quantifiers

• ?

Quantifiers apply to the thing immediately to the left of them.

In this case it is the single character x to the left of the quantifier, but later we'll see it can apply to a character-class or to a sub-expression enclosed in parentheses as well. Whatever is located immediately to the left of the quantifier.

r'ax*a'      # aa, axa, axxa, axxxa, ...
r'ax+a'      #     axa, axxa, axxxa, ...
r'ax?a'      # aa, axa
r'ax{2,4}a'  #          axxa, axxxa, axxxxa
r'ax{3,}a'   #                axxxa, axxxxa, ...
r'ax{17}a'   #                                 axxxxxxxxxxxxxxxxxa

| * | 0- | | + | 1- | | ? | 0-1 | | {n,m} | n-m | | {n,} | n- | | {n} | n |