Validating with an XML schema in Python

Question

I have an XML file and an XML schema in another file and I d like to validate that my XML file adheres to the schema   How do I do this in Python   I d prefer something using the standard library  but I can install a third-party package if necessary

User · Answer

You can easily validate an XML file or tree against an XML Schema (XSD) with the xmlschema Python package. It's pure Python, available on PyPi and doesn't have many dependencies.

Example - validate a file:

import xmlschema
xmlschema.validate('doc.xml', 'some.xsd')

The method raises an exception if the file doesn't validate against the XSD. That exception then contains some violation details.

If you want to validate many files you only have to load the XSD once:

xsd = xmlschema.XMLSchema('some.xsd')
for filename in filenames:
    xsd.validate(filename)

If you don't need the exception you can validate like this:

if xsd.is_valid('doc.xml'):
    print('do something useful')

Alternatively, xmlschema directly works on file objects and in memory XML trees (either created with xml.etree.ElementTree or lxml). Example:

import xml.etree.ElementTree as ET
t = ET.parse('doc.xml')
result = xsd.is_valid(t)
print('Document is valid? {}'.format(result))

User · Answer

An example of a simple validator in Python3 using the popular library lxml  Installation lxml  pip install lxml   If you get an error like  Could not find function xmlCheckVersion in library libxml2  Is libxml2 installed    try to do this first     Debian Ubuntu apt-get install python-dev python3-dev libxml2-dev libxslt-dev    Fedora 23  dnf install python-devel python3-devel libxml2-devel libxslt-devel     The simplest validator  Let s create simplest validator py  from lxml import etree  def validate xml path  str  xsd path  str  - gt  bool       xmlschema doc   etree parse xsd path      xmlschema   etree XMLSchema xmlschema doc       xml doc   etree parse xml path      result   xmlschema validate xml doc       return result   then write and run main py  from validator import validate  if validate  path to file xml    path to scheme xsd        print  Valid       else      print  Not valid           A little bit of OOP  In order to validate more than one file  there is no need to create an XMLSchema object every time  therefore   validator py  from lxml import etree  class Validator       def   init   self  xsd path  str           xmlschema doc   etree parse xsd path          self xmlschema   etree XMLSchema xmlschema doc       def validate self  xml path  str  - gt  bool          xml doc   etree parse xml path          result   self xmlschema validate xml doc           return result   Now we can validate all files in the directory as follows   main py  import os from validator import Validator  validator   Validator  path to scheme xsd      The directory with XML files XML DIR    path to directory   for file name in os listdir XML DIR       print        format file name   end          file path           format XML DIR  file name       if validator validate file path           print  Valid           else          print  Not valid           For more options read here  Validation with lxml

User · Answer

I am assuming you mean using XSD files  Surprisingly there aren t many python XML libraries that support this  lxml does however  Check Validation with lxml  The page also lists how to use lxml to validate with other schema types

User · Answer

I am assuming you mean using XSD files  Surprisingly there aren t many python XML libraries that support this  lxml does however  Check Validation with lxml  The page also lists how to use lxml to validate with other schema types

User · Answer

lxml provides etree DTD  from the tests on http   lxml de api lxml tests test dtd-pysrc html      root   etree XML  bytes   lt b  gt      dtd   etree DTD BytesIO   lt  ELEMENT b EMPTY gt      self assert  dtd validate root

User · Answer

There are two ways actually there are more  that you could do this  1  using lxml pip install lxml      from lxml import etree  objectify from lxml etree import XMLSyntaxError  def xml validator some xml string  xsd file   path to my schema file xsd        try          schema   etree XMLSchema file xsd file          parser   objectify makeparser schema schema          objectify fromstring some xml string  parser          print  YEAH   my xml file has validated      except XMLSyntaxError           handle exception here         print  Oh NO   my xml file does not validate          pass  xml file   open  my xml file xml    r   xml string   xml file read   xml file close    xml validator xml string    path to my schema file xsd      Use xmllint from the commandline  xmllint comes installed in many linux distributions     gt  gt  xmllint --format --pretty 1 --load-trace --debug --schema  path to my schema file xsd  path to my xml file xml

User · Answer

The PyXB package at http   pyxb sourceforge net  generates validating bindings for Python from XML schema documents   It handles almost every schema construct and supports multiple namespaces

User · Answer

The PyXB package at http   pyxb sourceforge net  generates validating bindings for Python from XML schema documents   It handles almost every schema construct and supports multiple namespaces

User · Answer

I am assuming you mean using XSD files  Surprisingly there aren t many python XML libraries that support this  lxml does however  Check Validation with lxml  The page also lists how to use lxml to validate with other schema types

User · Answer

As for  pure python  solutions  the package index lists    pyxsd  the description says it uses xml etree cElementTree  which is not  pure python   but included in stdlib   but source code indicates that it falls back to xml etree ElementTree  so this would count as pure python  Haven t used it  but according to the docs  it does do schema validation  minixsv   a lightweight XML schema validator written in  pure  Python   However  the description says  currently a subset of the XML schema standard is supported   so this may not be enough  XSV  which I think is used for the W3C s online xsd validator  it still seems to use the old pyxml package  which I think is no longer maintained

User · Answer

There are two ways actually there are more  that you could do this  1  using lxml pip install lxml      from lxml import etree  objectify from lxml etree import XMLSyntaxError  def xml validator some xml string  xsd file   path to my schema file xsd        try          schema   etree XMLSchema file xsd file          parser   objectify makeparser schema schema          objectify fromstring some xml string  parser          print  YEAH   my xml file has validated      except XMLSyntaxError           handle exception here         print  Oh NO   my xml file does not validate          pass  xml file   open  my xml file xml    r   xml string   xml file read   xml file close    xml validator xml string    path to my schema file xsd      Use xmllint from the commandline  xmllint comes installed in many linux distributions     gt  gt  xmllint --format --pretty 1 --load-trace --debug --schema  path to my schema file xsd  path to my xml file xml

User · Answer

An example of a simple validator in Python3 using the popular library lxml  Installation lxml  pip install lxml   If you get an error like  Could not find function xmlCheckVersion in library libxml2  Is libxml2 installed    try to do this first     Debian Ubuntu apt-get install python-dev python3-dev libxml2-dev libxslt-dev    Fedora 23  dnf install python-devel python3-devel libxml2-devel libxslt-devel     The simplest validator  Let s create simplest validator py  from lxml import etree  def validate xml path  str  xsd path  str  - gt  bool       xmlschema doc   etree parse xsd path      xmlschema   etree XMLSchema xmlschema doc       xml doc   etree parse xml path      result   xmlschema validate xml doc       return result   then write and run main py  from validator import validate  if validate  path to file xml    path to scheme xsd        print  Valid       else      print  Not valid           A little bit of OOP  In order to validate more than one file  there is no need to create an XMLSchema object every time  therefore   validator py  from lxml import etree  class Validator       def   init   self  xsd path  str           xmlschema doc   etree parse xsd path          self xmlschema   etree XMLSchema xmlschema doc       def validate self  xml path  str  - gt  bool          xml doc   etree parse xml path          result   self xmlschema validate xml doc           return result   Now we can validate all files in the directory as follows   main py  import os from validator import Validator  validator   Validator  path to scheme xsd      The directory with XML files XML DIR    path to directory   for file name in os listdir XML DIR       print        format file name   end          file path           format XML DIR  file name       if validator validate file path           print  Valid           else          print  Not valid           For more options read here  Validation with lxml

User · Answer

lxml provides etree DTD  from the tests on http   lxml de api lxml tests test dtd-pysrc html      root   etree XML  bytes   lt b  gt      dtd   etree DTD BytesIO   lt  ELEMENT b EMPTY gt      self assert  dtd validate root

User · Answer

I am assuming you mean using XSD files  Surprisingly there aren t many python XML libraries that support this  lxml does however  Check Validation with lxml  The page also lists how to use lxml to validate with other schema types

User · Answer

lxml provides etree DTD  from the tests on http   lxml de api lxml tests test dtd-pysrc html      root   etree XML  bytes   lt b  gt      dtd   etree DTD BytesIO   lt  ELEMENT b EMPTY gt      self assert  dtd validate root

User · Answer

lxml provides etree DTD  from the tests on http   lxml de api lxml tests test dtd-pysrc html      root   etree XML  bytes   lt b  gt      dtd   etree DTD BytesIO   lt  ELEMENT b EMPTY gt      self assert  dtd validate root

User · Answer

As for  pure python  solutions  the package index lists    pyxsd  the description says it uses xml etree cElementTree  which is not  pure python   but included in stdlib   but source code indicates that it falls back to xml etree ElementTree  so this would count as pure python  Haven t used it  but according to the docs  it does do schema validation  minixsv   a lightweight XML schema validator written in  pure  Python   However  the description says  currently a subset of the XML schema standard is supported   so this may not be enough  XSV  which I think is used for the W3C s online xsd validator  it still seems to use the old pyxml package  which I think is no longer maintained

User · Answer

You can easily validate an XML file or tree against an XML Schema (XSD) with the xmlschema Python package. It's pure Python, available on PyPi and doesn't have many dependencies.

Example - validate a file:

import xmlschema
xmlschema.validate('doc.xml', 'some.xsd')

The method raises an exception if the file doesn't validate against the XSD. That exception then contains some violation details.

If you want to validate many files you only have to load the XSD once:

xsd = xmlschema.XMLSchema('some.xsd')
for filename in filenames:
    xsd.validate(filename)

If you don't need the exception you can validate like this:

if xsd.is_valid('doc.xml'):
    print('do something useful')

Alternatively, xmlschema directly works on file objects and in memory XML trees (either created with xml.etree.ElementTree or lxml). Example:

import xml.etree.ElementTree as ET
t = ET.parse('doc.xml')
result = xsd.is_valid(t)
print('Document is valid? {}'.format(result))

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