Prerequisites: BeautifulSoup
Beautifulsoup is a Python library used for web scraping. This powerful python tool can also be used to modify html webpages. This article depicts how beautifulsoup can be employed to modify the parse tree. BeautifulSoup is used to search the parse tree and allow you to modify the tree. You can rename tag, change the values of its attributes, add and delete attribute.
Modifying the name of the tag and its attributes
You can change the name of the tag and modify its attribute by adding or deleting them.
- To change tag name:
Syntax: tag.name = “new_tag”
- To modify its attribute or to add new attribute:
Syntax: tag[“attribute”] = “value”
- To delete any attribute:
Syntax: del tag[“attribute”]
A tree can also be modified by inserting new elements at required places.
- insert() function will insert new element at any position
Syntax: tag.insert()
- insert_after() function will insert element after something in the parse tree.
Syntax: tag.insert_after()
- insert_before() function will insert element before something in the parse tree.
Syntax: tag.insert_before()
Approach :
- Import module
- Scrap data from webpage
- Parse the string scraped to html
- Select tag within which modification has to be performed
- Make required changes
Example 1:
# importing modulefrom bs4 import BeautifulSoup
markup = """<p class="para">gfg</p>
"""# parsering string to HTMLsoup = BeautifulSoup(markup, 'html.parser')
# extracting a tagtag = soup.p
print("Before modifying the tag name: ")
print(tag)
print()
# modifying tag nametag.name = "div"
print("After modifying the tag name: ")
print(tag)
print()
# modifying its class attributetag['class'] = "div_class"
# adding new attributetag['id'] = "div_id"
print("After modifying and adding attributes: ")
print(tag)
print()
# to delete any attributesdel tag["class"]
print("After deleting class attribute: ")
print(tag)
print()
# modifying the tags contenttag.string = "Geeks"
print("After modifying tag string: ")
print(tag)
print()
# using insert function.tag = soup.div
print("Before inserting: ")
print(tag)
print()
# inserting contenttag.insert(1, " for Geeks")
print("After inserting: ")
print(tag)
print()
|
Output:
Example 2:
# importing modulefrom bs4 import BeautifulSoup
soup = BeautifulSoup("<b>| A Computer Science portal</b>", 'html.parser')
tag = soup.new_tag("p")
tag.string = "Geeks"
# insert beforesoup.b.string.insert_before(tag)print(soup.b)
print()
# insert aftersoup.b.p.insert_after(soup.new_string(" for Geeks"))
print(soup.b)
|
Output:
Adding new tag and wrapping element
The tree can be modified by adding a new tag at any required location. We can also wrap the element to modify it.
- new_tag() function will add a new tag
Syntax: new_tag(“attribute”)
- wrap() function will enclose an element in the tag you specify and returns a new wrapper
Syntax: wrap()
- unwrap() function unwrap the wrapped elements.
Syntax: unwrap()
Example:
# importing modulefrom bs4 import BeautifulSoup
markup = '
<p>Geeks for Geeks</p>
'# parsering string to HTMLsoup = BeautifulSoup(markup, 'html.parser')
print(soup)
# wrapping around the stringsoup.p.string.wrap(soup.new_tag("i"))
print(soup)
# wrapping around the tagsoup.p.wrap(soup.new_tag("div"))
print(soup)
# unwrapping the i tagsoup.p.i.unwrap()print(soup)
old_tag = soup.div
# new tagnew_tag = soup.new_tag('div')
new_tag.string = "| A Computer Science portal for geeks"
# adding new tagold_tag.append(new_tag)print(soup)
|
Output:
Replacing element
replace_with() function will replace old tag or string with new tag or string in the parse tree.
Syntax: replace_with()
Example:
# importing BeautifulSoup Modulefrom bs4 import BeautifulSoup
# parsering string to HTMLsoup = BeautifulSoup(markup, 'html.parser')
# tag to be replacedold_tag = soup.a
# new tagnew_tag = soup.new_tag("p")
# input stringnew_tag.string = "gfg.in"
'''replacing tag page_element.replace_with("string") removes a tag or string from the tree, and replacesit with the tag or string of your choice.'''old_tag.i.replace_with(new_tag)print(old_tag)
|
Output:
<a href=”http://gfg.com/”>Geeks for Geeks <p>gfg.in</p></a>
Adding new content to an existing tag
For adding new contents to an existing tag can be done by append() function or NavigableString() constructor.
Syntax: tag.append(“content”)
Example:
# importing modulefrom bs4 import BeautifulSoup
from bs4 import NavigableString
# parsering string to HTMLsoup = BeautifulSoup(markup, 'html.parser')
# extracting a tagtag = soup.a
# appending contenttag.append("| A Computer Science portal")
print(tag)
# appending content using navigableString constructornew_str = NavigableString(" for geeks")
tag.append(new_str)print(tag)
|
Output:
<a href=”https://www.geeksforgeeks.org/”>Geeks for Geeks| A Computer Science portal</a>
<a href=”https://www.geeksforgeeks.org/”>Geeks for Geeks| A Computer Science portal for geeks</a>
Removing content and element
A tree can be modified by removing content from it or by removing element also.
- clear() removes the contents of the tag.
Syntax: clear()
- extract() removes a tag or strings from the tree.
Syntax: extract()
- decompose() removes the tag and delete it all content.
Syntax: decompose()
Example:
# importing modulefrom bs4 import BeautifulSoup
markup = '<a href="https://www.geeksforgeeks.org/">Geeks for Geeks <i>| A Computer Science portal</i></a>'
# parsering string to HTMLsoup = BeautifulSoup(markup, 'html.parser')
tag = soup.a
print(tag)
print()
# clearing its all contenttag.clear()print(tag)
print()
# extracting i tag# parsering string to HTMLsoup2 = BeautifulSoup(markup, 'html.parser')
a_tag = soup2.a
print(a_tag)
print()
i_tag = soup2.i.extract()
print(a_tag)
print()
# decomposing i tag# parsering string to HTMLsoup2 = BeautifulSoup(markup, 'html.parser')
a_tag = soup2.a
print(a_tag)
print()
i_tag = soup2.i.decompose()
print(a_tag)
|
Output: