"Web crawler" prep knowledge

"Web crawler" prep knowledge

I. Expressions commonly used in regular expressions

There are a lot of things in regular expression, it is difficult to learn fine, but do not need to learn fine crawler, as long as it will be part of the line, the following will introduce my commonly used expressions, basic enough.

1. Go head to Tail---(<= ...) ... (?=...)

The expression is the most I use, such as test instructions, go to the end of the head to match the middle, matching a single data is very useful, is good to write, easy to understand, and the match out of the thing is want

2. Group---(?< group name; ）...

This expression is primarily used when matching multiple data with a regular

It's going to be 2 basic.

Two. Grab the bag tool, do the crawler this is essential, no tools are basically not done

It is recommended to bring your own F12 to IE11.

There are no bags that can't be caught, and the search function is also very powerful.

"Web crawler" prep knowledge