The Django Book Chapter 9 - Django Workshop - Taipei.py

1. Advanced Templates 2013-07-23. Django Workshop.

2. About me • TP (@uranusjr) • RTFD • Find me anywhere

3. Language Review {% if is_logged_in %}! Thanks for logging in!! {% else %}! Welcome to {{ website_name }}.! {% endif %}

4. Template tags {% if is_logged_in %}! Thanks for logging in!! {% else %}! Welcome to {{ website_name }}.! {% endif %}

5. Variables {% if is_logged_in %}! Thanks for logging in!! {% else %}! Welcome to {{ website_name }}.! {% endif %}

6. Language Review • Variables come from a context • Dictionary-like name-value mapping • A context is rendered by the template • Variable replacement • Template tag execution

7. Template __init__(self, string) render(self, context) format string context rendered value text ﬁle dict object

8. from django.shortcuts import render_to_response! ! def view_1(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am view 1.'! }! return render_to_response('template1.html',! context_dict)! ! def view_2(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am the second view.'! }! return render_to_response('template2.html',! context_dict)

9. from django.shortcuts import render_to_response! ! def view_1(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am view 1.'! }! return render_to_response('template1.html',! context_dict)! ! def view_2(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am the second view.'! }! return render_to_response('template2.html',! context_dict)

10. from django.template import loader, Context! ! def view_1(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am view 1.'! }! t = loader.get_template('template1.html')! context = Context(context_dict)! return t.render(context)! ! def view_2(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am the second view.'! }! t = loader.get_template('template2.html')! context = Context(context_dict)! return t.render(context)

11. from django.template import loader, Context! ! def view_1(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am view 1.'! }! t = loader.get_template('template1.html')! context = Context(context_dict)! return t.render(context)! ! def view_2(request):! context_dict = {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR'],! 'message': 'I am the second view.'! }! t = loader.get_template('template2.html')! context = Context(context_dict)! return t.render(context)

12. from django.template import loader, Context! ! def render_it(template, context_dict):! context_dict.update({! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! })! return template.render(Context(context_dict))! ! def view_1(request):! t = loader.get_template('template1.html')! context_dict = {'message': 'I am view 1.'}! return render_it(t, context_dict)! ! def view_2(request):! t = loader.get_template('template2.html')! context_dict = {! 'message': 'I am the second view.'! }! return render_it(t, context_dict)

13. from django.template import loader, Context! ! def render_it(template, context_dict):! context_dict.update({! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! })! return template.render(Context(context_dict))! ! def view_1(request):! t = loader.get_template('template1.html')! context_dict = {'message': 'I am view 1.'}! return render_it(t, context_dict)! ! def view_2(request):! t = loader.get_template('template2.html')! context_dict = {! 'message': 'I am the second view.'! }! return render_it(t, context_dict)

14. from django.template import loader, RequestContext! ! def custom_proc(request):! return {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! }! ! def view_1(request):! t = loader.get_template('template1.html')! context = RequestContext(! request, {'message': 'I am view 1.'},! processors=[custom_proc]! )! return t.render(context)! ! def view_2(request):! t = loader.get_template('template2.html')! context = RequestContext(! request, {'message': 'I am the second view.'},! processors=[custom_proc]! )! return t.render(context)

17. from django.shortcuts import render_to_response! from django.template import RequestContext! ! def custom_proc(request):! return {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! }! ! def view_1(request):! context = RequestContext(request, processors=[custom_proc])! return render_to_response(! 'template1.html',! {'message': 'I am view 1.'},! context_instance=context! )! ! def view_2(request):! context = RequestContext(request, processors=[custom_proc])! return render_to_response(! 'template2.html',! {'message': 'I am the second view.'},! context_instance=context! )

18. from django.shortcuts import render_to_response! from django.template import RequestContext! ! def custom_proc(request):! return {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! }! ! def view_1(request):! context = RequestContext(request, processors=[custom_proc])! return render_to_response(! 'template1.html',! {'message': 'I am view 1.'},! context_instance=context! )! ! def view_2(request):! context = RequestContext(request, processors=[custom_proc])! return render_to_response(! 'template2.html',! {'message': 'I am the second view.'},! context_instance=context! )

19. TEMPLATE_CONTEXT_PROCESSORS = (! 'django.contrib.auth.context_processors.auth',! 'django.core.context_processors.debug',! 'django.core.context_processors.i18n',! 'django.core.context_processors.media',! 'django.core.context_processors.static',! 'django.core.context_processors.tz',! 'django.contrib.messages.context_processors.messages',! 'myapp.views.custom_proc'! ) settings.py

20. TEMPLATE_CONTEXT_PROCESSORS = (! 'django.contrib.auth.context_processors.auth',! 'django.core.context_processors.debug',! 'django.core.context_processors.i18n',! 'django.core.context_processors.media',! 'django.core.context_processors.static',! 'django.core.context_processors.tz',! 'django.contrib.messages.context_processors.messages',! 'myapp.views.custom_proc'! ) settings.py

21. from django.shortcuts import render_to_response! from django.template import RequestContext! ! def custom_proc(request):! return {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! }! ! def view_1(request):! context = RequestContext(request)! return render_to_response(! 'template1.html',! {'message': 'I am view 1.'},! context_instance=context! )! ! def view_2(request):! context = RequestContext(request)! return render_to_response(! 'template2.html',! {'message': 'I am the second view.'},! context_instance=context! )

22. from django.shortcuts import render_to_response! from django.template import RequestContext! ! def custom_proc(request):! return {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! }! ! def view_1(request):! context = RequestContext(request)! return render_to_response(! 'template1.html',! {'message': 'I am view 1.'},! context_instance=context! )! ! def view_2(request):! context = RequestContext(request)! return render_to_response(! 'template2.html',! {'message': 'I am the second view.'},! context_instance=context! )

23. from django.shortcuts import render! ! def custom_proc(request):! return {! 'app': 'My app',! 'user': request.user,! 'ip_address': request.META['REMOTE_ADDR']! }! ! def view_1(request):! return render(! 'template1.html',! {'message': 'I am view 1.'}! )! ! def view_2(request):! return render(! 'template2.html',! {'message': 'I am the second view.'}! )

24. Custom Processors • Do one thing and do it well • Pick your variable names •Context keys are global • General import conventions apply

25. • Breaking down render_to_response • RequestContext and context processors • TEMPLATE_CONTEXT_PROCESSORS • django.shortcuts.render Summary

26. HTML Escaping • Variable values are escaped by default • {{ something|safe }} • {% autoescape off %}  Not escaped: {{ something }}  {% endautoescape %}! • Literals in tags/ﬁlters are not escaped • {{ escaped|default:'1 < 2' }}

27. Template Loading • django.template.loader • get_template(template_name) • select_template(template_names)! • TemplateDoesNotExist! • TEMPLATE_DIRS! • TEMPLATE_LOADERS

28. PROJECT_ROOT = …! ! ! TEMPLATE_DIRS = (! os.path.join(PROJECT_ROOT, 'templates'),! os.path.join(PROJECT_ROOT, 'other_templates')! )! ! TEMPLATE_LOADERS = (! 'django.template.loaders.filesystem.Loader',! 'django.template.loaders.app_directories.Loader',! # 'django.template.loaders.eggs.Loader',! )

29. 1 2 3 • Loader order • Path order • Third-party apps will be searched • App directory search order is undeﬁned

30. Questions?

32. Template Tags

33. Before We Start... • This is a HUGE topic • Read the documentation • Learn how others do it • Template processing is string manipulation • Slow, period • No fancy things unless necessary

34. Template Library

35. Template Library

36. Template Library Name matters

37. Template Library Don’t forget this

38. Template Library Naming is important

39. Template Filter • Takes one or zero arguments • Always returns something • Fails silently

40. {{ value|upper }}! ! {{ value|add:arg }}

41. from django import template! ! register = template.Library()! ! ! def upper(value):! """Converts a string into all uppercase."""! return value.upper()! ! ! def add(value, arg):! """Adds the arg to the value."""! return int(value) + int(arg)

42. from django import template! ! register = template.Library()! ! ! def upper(value):! """Converts a string into all uppercase."""! return value.upper()! ! ! def add(value, arg):! """Adds the arg to the value."""! return int(value) + int(arg)

43. from django import template! ! register = template.Library()! ! ! def upper(value):! """Converts a string into all uppercase."""! return value.upper()! ! ! def add(value, arg):! """Adds the arg to the value."""! return int(value) + int(arg)! ! ! register.filter('upper', upper)! register.filter('add', add)

44. from django import template! ! register = template.Library()! ! ! @register.filter(name='upper')! def upper(value):! """Converts a string into all uppercase."""! return value.upper()! ! ! @register.filter(name='add')! def add(value, arg):! """Adds the arg to the value."""! return int(value) + int(arg)!

45. from django import template! ! register = template.Library()! ! ! @register.filter! def upper(value):! """Converts a string into all uppercase."""! return value.upper()! ! ! @register.filter! def add(value, arg):! """Adds the arg to the value."""! return int(value) + int(arg)!

46. @register.filter! def upper(value):! """Converts a string into all uppercase."""! return value.upper()! ! ! @register.filter! def add(value, arg):! """Adds the arg to the value."""! try:! return int(value) + int(arg)! except (ValueError, TypeError):! try:! return value + arg! except Exception:! return '' # Return something

47. @register.filter! def upper(value):! """Converts a string into all uppercase."""! return value.upper() # Let it fail! ! ! @register.filter! def add(value, arg):! """Adds the arg to the value."""! try:! return int(value) + int(arg)! except (ValueError, TypeError):! try:! return value + arg! except Exception:! return ''

48. {{ value|upper }}! ! {{ value|add:arg }}

49. {% load myapp_tags %}! ! {{ value|upper }}! ! {{ value|add:arg }}

50. {{ value|date:arg }}

51. from django.conf import settings! from django.utils import formats! ! @register.filter! def date(value, arg=None):! """Formats a date according to the given format."""! if value in (None, ''):! return ''! if arg is None:! arg = settings.DATE_FORMAT! try:! return formats.date_format(value, arg)! except AttributeError:! try:! return format(value, arg)! except AttributeError:! return ''

55. Return Something •Not necessarily a string •Only need to be convertible to a string • None is converted to 'None', not '' •I always return strings

56. Template Tags Compilation function Template tag node __init__(self, string) render(self, context) template context rendered value

57. {% now format_string %}

58. from django import template! from django.template import TemplateSyntaxError! ! register = template.Library()! ! ! @register.tag! def now(parser, token):! bits = token.split_contents()! if len(bits) != 2:! raise TemplateSyntaxError(! "'now' statement takes one argument"! )! format_string = bits[1][1:-1]! return NowNode(format_string)!

64. from datetime import datetime! ! ! class NowNode(Node):! def __init__(self, format_string):! self.format_string = format_string! ! def render(self, context):! now = datetime.now()! return now.strftime(self.format_string)

65. from datetime import datetime! ! ! class NowNode(Node):! def __init__(self, format_string):! self.format_string = format_string! ! def render(self, context):! now = datetime.now()! return now.strftime(self.format_string)

66. from datetime import datetime! from django.conf import settings! from django.template.defaultfilters import date! from django.utils import timezone! ! ! class NowNode(Node):! def __init__(self, format_string):! self.format_string = format_string! ! def render(self, context):! if settings.USE_TZ:! tzinfo = timezone.get_current_timezone()! else:! tzinfo = None! return date(! datetime.now(tz=tzinfo),! self.format_string! )

67. from datetime import datetime! from django.conf import settings! from django.template.defaultfilters import date! from django.utils import timezone! ! ! class NowNode(Node):! def __init__(self, format_string):! self.format_string = format_string! ! def render(self, context):! if settings.USE_TZ:! tzinfo = timezone.get_current_timezone()! else:! tzinfo = None! return date(! datetime.now(tz=tzinfo),! self.format_string! )

68. {% inject_now format_string %}! ! <p>The time is {{ now }}</p>

69. from django import template! from django.template import TemplateSyntaxError! ! register = template.Library()! ! ! @register.tag! def inject_now(parser, token):! bits = token.split_contents()! if len(bits) != 2:! raise TemplateSyntaxError(! "'inject_now' requires one argument"! )! format_string = bits[1][1:-1]! return InjectNowNode(format_string)!

70. class InjectNowNode(Node):! def __init__(self, format_string):! self.format_string = format_string! ! def render(self, context):! if settings.USE_TZ:! tzinfo = timezone.get_current_timezone()! else:! tzinfo = None! context['now'] = date(! datetime.now(tz=tzinfo),! self.format_string! )! return ''

71. class InjectNowNode(Node):! def __init__(self, format_string):! self.format_string = format_string! ! def render(self, context):! if settings.USE_TZ:! tzinfo = timezone.get_current_timezone()! else:! tzinfo = None! context['now'] = date(! datetime.now(tz=tzinfo),! self.format_string! )! return ''

72. {% inject_now format_string as var_name %}! ! <p>The time now is {{ var_name }}</p>

73. @register.tag! def inject_now(parser, token):! bits = token.split_contents()! if len(bits) != 4:! raise TemplateSyntaxError(! "'inject_now' statement requires form "! "{% inject_now format as var_name %}."! )! format_string = bits[1][1:-1]! var_name = bits[3]! return InjectNowNode(format_string, var_name)

74. @register.tag! def inject_now(parser, token):! error = TemplateSyntaxError(! "'inject_now' statement requires form "! "{% inject_now format as var_name %}."! )! try:! tag_name, arg = token.contents.split(None, 1)! except ValueError:! raise error! ! m = re.search(r'(.*?) as (w+)', arg)! if m:! fmt, var_name = m.groups()! else:! raise error! if not (fmt[0] == fmt[-1] and fmt[0] in ('"', "'")):! raise error! ! return InjectNowNode(fmt[1:-1], var_name)

75. class InjectNowNode(Node):! def __init__(self, format_string, var_name):! self.format_string = format_string! self.var_name = var_name! ! def render(self, context):! if settings.USE_TZ:! tzinfo = timezone.get_current_timezone()! else:! tzinfo = None! context[self.var_name] = date(! datetime.now(tz=tzinfo),! self.format_string! )! return ''

76. Start-end tags • parser.parse(end_tags_tuple)! • Returns a NodeList instance (iterable) • parser.delete_first_token() • Deletes next token (i.e. the end token)

77. def do_comment(parser, token):! nodelist = parser.parse(('endcomment',))! parser.delete_first_token()! return CommentNode()! ! ! class CommentNode(template.Node):! def render(self, context):! return ''

80. Shortcuts • register.simple_tag • register.inclusion_tag(template)! • takes_context=True! • stringfilter

81. Custom Loaders • implement load_template_source • Raise TemplateDoesNotExist when appropriate • Add it to TEMPLATE_LOADERS in settings

82. Standalone Mode • django.conf.settings.configure() • I’d just use another template engine • Jinja2 + Cofﬁn • Read Appendix D or the docs if you really know what you’re doing

83. Again... • This is a HUGE topic • Read the documentation • Learn how others do it • Template processing is string manipulation • Slow, period • No fancy things unless necessary

84. Questions?

The Django Book Chapter 9 - Django Workshop - Taipei.py

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