BeautifulSoup prettify() modifies significant whitespace even if the attribute xml:space is set to "preserve".
Example xml file with significant whitespace:
<svg viewBox="0 0 160 50" xmlns="http://www.w3.org/2000/svg">
<text y="20" xml:space="default"> Default spacing</text>
<text y="40" xml:space="preserve"> <tspan>reserved spacing</tspan></text>
</svg>
Code:
from bs4 import BeautifulSoup
xml_string_with_significant_whitespace ='''
<svg viewBox="0 0 160 50" xmlns="http://www.w3.org/2000/svg">
<text y="20" xml:space="default"> Default spacing</text>
<text y="40" xml:space="preserve"> <tspan>reserved spacing</tspan></text>
</svg>
'''
soup = BeautifulSoup(xml_string_with_significant_whitespace, "xml")
# no modifications made
print(soup.prettify()) # modifies significant whitespace
# print(str(soup)) # doesn't modify significant whitespace
Output:
<svg viewBox="0 0 160 50" xmlns="http://www.w3.org/2000/svg">
<text xml:space="default" y="20">
Default spacing
</text>
<text xml:space="preserve" y="40">
<tspan>
reserved spacing
</tspan>
</text>
</svg>
Text will be moved due to modified whitespace.
How do I prevent prettify() from changing the meaning of the xml file, instead of just changing the layout?
As MendelG expained in his answer BeautifulSoup prettify() does change the meaning of documents and prettify() is only meant as an aid for readability.
I wanted a solution that would reformat the document without changing its meaning and with the least amount of changes.
The following code prettifies xml without modifying significant whitespace (xml:space="preserve"), CDATA and XML declarations:
import xml.sax
from io import StringIO
import re
import sys
class Prettifier(xml.sax.ContentHandler, xml.sax.handler.LexicalHandler):
def __init__(self, print_method=None):
self.level = -1
self.preserve_space_stack=[False]
self.last_was_opening_tag = False #tags without content or empty content don't need closing tag on next line
self.indent = " "*4
self.first_tag = True
self.external_print_method = print_method
self.string=""
self.CDATA = False
def get_string(self):
return self.string
def print_method(self, text="", end="\n"):
if self.external_print_method:
self.external_print_method(text, end)
self.string += text + end
# Call when an element starts
def startElement(self, tag, attributes):
self.level += 1
if 'xml:space' in attributes:
self.preserve_space_stack.append(attributes['xml:space'] == 'preserve')
else:
self.preserve_space_stack.append(self.preserve_space_stack[-1])
attributes_string = " ".join([f'{key}="{value}"' for key,value in attributes.items()])
if self.preserve_space_stack[-1]:
if self.preserve_space_stack[-2] == False:
self.print_method()
self.print_method(self.indent*self.level, end="")
self.print_method(f"<{tag}", end="")
self.print_method(" "*(len(attributes_string)!=0), end="")
self.print_method(attributes_string, end="")
self.print_method(">", end="")
else:
if not self.first_tag:
self.print_method()
if len(attributes_string) > 60:
attributes_string = f"\n{self.indent*self.level + ' '*(len(tag)+2)}".join([f'{key}="{value}"' for key,value in attributes.items()])
self.print_method(self.indent*self.level, end="")
self.print_method(f"<{tag}", end="")
self.print_method(" "*(len(attributes_string)!=0), end="")
self.print_method(attributes_string, end="")
self.print_method(">", end="")
self.last_was_opening_tag = True
self.first_tag = False
# Call when an elements ends
def endElement(self, tag):
if self.preserve_space_stack[-1]:
self.print_method(f"</{tag}", end="")
self.print_method(">", end="")
else:
if not self.last_was_opening_tag:
self.print_method()
self.print_method(self.indent*self.level, end="")
self.print_method(f"</{tag}", end="")
self.print_method(">",end="")
self.level -= 1
self.preserve_space_stack.pop()
self.last_was_opening_tag = False
# Call when a character is read
def characters(self, content):
if self.CDATA:
self.print_method(content, end="")
else:
empty_content = False
if self.preserve_space_stack[-1]:
self.print_method(content, end="")
empty_content = content == ""
else:
empty_content = content.strip() == ""
if not empty_content:
self.print_method()
self.print_method(self.indent*(self.level+1), end="")
self.print_method(content.strip(), end="")
self.last_was_opening_tag = self.last_was_opening_tag and empty_content
# lexical handler methods:
def comment(self, content):
if not self.preserve_space_stack[-1]:
self.print_method()
self.print_method(self.indent*(self.level+1), end="")
self.print_method(f"<!--{content}-->", end="")
def startCDATA(self):
#The contents of the CDATA marked section will be reported through the characters handler.
if not self.preserve_space_stack[-1]:
self.print_method()
self.print_method(self.indent*(self.level+1), end="")
self.print_method("<![CDATA[", end="")
self.CDATA = True
def endCDATA(self):
self.print_method("]]>", end="")
self.CDATA = False
def process_xml_declaration(xml_string):
declaration = ""
regex = r"^\s*(<\?xml [^\?>]*\?>)"
matches = re.search(regex, xml_string)
if matches:
declaration = matches.group(1) + "\n"
return declaration
def prettify_file(file_name):
Handler = Prettifier()
parser = xml.sax.make_parser()
parser.setFeature(xml.sax.handler.feature_namespaces, 0)# turn off namespaces
parser.setContentHandler(Handler)
parser.setProperty(xml.sax.handler.property_lexical_handler, Handler)
parser.parse(file_name)
declaration = ""
with open(file_name, 'r', encoding='utf8') as f:
declaration = process_xml_declaration(f.read())
return declaration + Handler.get_string()
def prettify_string(xml_string):
Handler = Prettifier()
parser = xml.sax.make_parser()
parser.setFeature(xml.sax.handler.feature_namespaces, 0)# turn off namespaces
parser.setContentHandler(Handler)
parser.setProperty(xml.sax.handler.property_lexical_handler, Handler)
xml_string_stream = StringIO(xml_string)
parser.parse(xml_string_stream)
declaration = process_xml_declaration(xml_string)
return declaration + Handler.get_string()
if __name__ == "__main__":
if len(sys.argv) > 1:
for bad_image_path in sys.argv[1:]:
svg_string_pretty = prettify_file(bad_image_path)
with open(bad_image_path, 'w', encoding='utf8', newline='\n') as f:
f.write(svg_string_pretty)
else:
pass