Python Natural Language Processing

Positive lookahead

Positive lookahead matches the substring from a string if the defined pattern is followed by the substring. If you don't understand, then let's look at the following example:

• Consider a sentence: I play on the playground.
• Now, you want to extract play as a pattern but only if it follows ground. In this situation, you can use positive lookahead.

The syntax of positive lookahead is (?=pattern)

The regex rplay(?=ground) matches play, but only if it is followed by ground. Thus, the first play in the text string won't be matched.