downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is some- what similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted regular expressions so lxml‘s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is somewhat similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted so lxml [http://lxml.de/]‘s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is some- what similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted regular expressions so lxml’s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is some- what similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted regular expressions so lxml’s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is some- what similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted regular expressions so lxml‘s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is somewhat similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted so lxml [http://lxml.de/]‘s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is somewhat similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted so lxml [http://lxml.de/]‘s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is somewhat similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted so lxml [http://lxml.de/]’s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is some- what similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted regular expressions so lxml’s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. Set operations These can be handy

downloaded by Scrapy and then their response handled by the specified callback. 3. In callback functions, you parse the page contents, typically using Selectors (but you can also use BeautifulSoup, lxml $somevariable syntax. This is somewhat similar to parameterized queries or prepared statements in the SQL world where you replace some arguments in your queries with placeholders like ?, which are then substituted regular expressions so lxml’s implementation uses hooks to Python’s re module. Thus, using regexp functions in your XPath expressions may add a small performance penalty. 58 Chapter 3. Basic concepts Scrapy