Template Designer Documentation - Jinja2 Documentation (2.10) - 0 views
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A Jinja template doesn’t need to have a specific extension
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A Jinja template is simply a text file
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tags, which control the logic of the template
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{% ... %} for Statements
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{{ ... }} for Expressions to print to the template output
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use a dot (.) to access attributes of a variable
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the outer double-curly braces are not part of the variable, but the print statement.
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If you access variables inside tags don’t put the braces around them.
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If a variable or attribute does not exist, you will get back an undefined value.
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the default behavior is to evaluate to an empty string if printed or iterated over, and to fail for every other operation.
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if an object has an item and attribute with the same name. Additionally, the attr() filter only looks up attributes.
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Variables can be modified by filters. Filters are separated from the variable by a pipe symbol (|) and may have optional arguments in parentheses.
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Multiple filters can be chained
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Tests can be used to test a variable against a common expression.
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add is plus the name of the test after the variable.
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to find out if a variable is defined, you can do name is defined, which will then return true or false depending on whether name is defined in the current template context.
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strip whitespace in templates by hand. If you add a minus sign (-) to the start or end of a block (e.g. a For tag), a comment, or a variable expression, the whitespaces before or after that block will be removed
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not add whitespace between the tag and the minus sign
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mark a block raw
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Template inheritance allows you to build a base “skeleton” template that contains all the common elements of your site and defines blocks that child templates can override.
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The {% extends %} tag is the key here. It tells the template engine that this template “extends” another template.
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access templates in subdirectories with a slash
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can’t define multiple {% block %} tags with the same name in the same template
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use the special self variable and call the block with that name
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self.title()
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super()
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put the name of the block after the end tag for better readability
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if the block is replaced by a child template, a variable would appear that was not defined in the block or passed to the context.
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setting the block to “scoped” by adding the scoped modifier to a block declaration
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If you have a variable that may include any of the following chars (>, <, &, or ") you SHOULD escape it unless the variable contains well-formed and trusted HTML.
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Jinja2 functions (macros, super, self.BLOCKNAME) always return template data that is marked as safe.
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With the default syntax, control structures appear inside {% ... %} blocks.
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the dictsort filter
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loop.cycle
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Unlike in Python, it’s not possible to break or continue in a loop
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use loops recursively
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add the recursive modifier to the loop definition and call the loop variable with the new iterable where you want to recurse.
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The loop variable always refers to the closest (innermost) loop.
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whether the value changed at all,
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use it to test if a variable is defined, not empty and not false
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Macros are comparable with functions in regular programming languages.
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If a macro name starts with an underscore, it’s not exported and can’t be imported.
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pass a macro to another macro
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caller()
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a single trailing newline is stripped if present
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other whitespace (spaces, tabs, newlines etc.) is returned unchanged
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a block tag works in “both” directions. That is, a block tag doesn’t just provide a placeholder to fill - it also defines the content that fills the placeholder in the parent.
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Python dicts are not ordered
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caller(user)
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call(user)
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This is a simple dialog rendered by using a macro and a call block.
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Filter sections allow you to apply regular Jinja2 filters on a block of template data.
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Assignments at top level (outside of blocks, macros or loops) are exported from the template like top level macros and can be imported by other templates.
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using namespace objects which allow propagating of changes across scopes
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use block assignments to capture the contents of a block into a variable name.
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The extends tag can be used to extend one template from another.
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Blocks are used for inheritance and act as both placeholders and replacements at the same time.
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The include statement is useful to include a template and return the rendered contents of that file into the current namespace
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Included templates have access to the variables of the active context by default.
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putting often used code into macros
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imports are cached and imported templates don’t have access to the current template variables, just the globals by default.
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Macros and variables starting with one or more underscores are private and cannot be imported.
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By default, included templates are passed the current context and imported templates are not.
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imports are often used just as a module that holds macros.
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Integers and floating point numbers are created by just writing the number down
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Everything between two brackets is a list.
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Tuples are like lists that cannot be modified (“immutable”).
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A dict in Python is a structure that combines keys and values.
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// Divide two numbers and return the truncated integer result
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The special constants true, false, and none are indeed lowercase
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all Jinja identifiers are lowercase
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(expr) group an expression.
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The is and in operators support negation using an infix notation
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in Perform a sequence / mapping containment test.
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| Applies a filter.
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~ Converts all operands into strings and concatenates them.
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use inline if expressions.
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always an attribute is returned and items are not looked up.
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default(value, default_value=u'', boolean=False)¶ If the value is undefined it will return the passed default value, otherwise the value of the variable
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dictsort(value, case_sensitive=False, by='key', reverse=False)¶ Sort a dict and yield (key, value) pairs.
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format(value, *args, **kwargs)¶ Apply python string formatting on an object
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groupby(value, attribute)¶ Group a sequence of objects by a common attribute.
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grouping by is stored in the grouper attribute and the list contains all the objects that have this grouper in common.
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indent(s, width=4, first=False, blank=False, indentfirst=None)¶ Return a copy of the string with each line indented by 4 spaces. The first line and blank lines are not indented by default.
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join(value, d=u'', attribute=None)¶ Return a string which is the concatenation of the strings in the sequence.
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map()¶ Applies a filter on a sequence of objects or looks up an attribute.
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pprint(value, verbose=False)¶ Pretty print a variable. Useful for debugging.
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reject()¶ Filters a sequence of objects by applying a test to each object, and rejecting the objects with the test succeeding.
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replace(s, old, new, count=None)¶ Return a copy of the value with all occurrences of a substring replaced with a new one.
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round(value, precision=0, method='common')¶ Round the number to a given precision
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even if rounded to 0 precision, a float is returned.
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select()¶ Filters a sequence of objects by applying a test to each object, and only selecting the objects with the test succeeding.
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sort(value, reverse=False, case_sensitive=False, attribute=None)¶ Sort an iterable. Per default it sorts ascending, if you pass it true as first argument it will reverse the sorting.
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striptags(value)¶ Strip SGML/XML tags and replace adjacent whitespace by one space.
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tojson(value, indent=None)¶ Dumps a structure to JSON so that it’s safe to use in <script> tags.
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trim(value)¶ Strip leading and trailing whitespace.
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unique(value, case_sensitive=False, attribute=None)¶ Returns a list of unique items from the the given iterable
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urlize(value, trim_url_limit=None, nofollow=False, target=None, rel=None)¶ Converts URLs in plain text into clickable links.
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defined(value)¶ Return true if the variable is defined
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in(value, seq)¶ Check if value is in seq.
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mapping(value)¶ Return true if the object is a mapping (dict etc.).
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number(value)¶ Return true if the variable is a number.
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sameas(value, other)¶ Check if an object points to the same memory address than another object
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undefined(value)¶ Like defined() but the other way round.
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A joiner is passed a string and will return that string every time it’s called, except the first time (in which case it returns an empty string).
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namespace(...)¶ Creates a new container that allows attribute assignment using the {% set %} tag
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The with statement makes it possible to create a new inner scope. Variables set within this scope are not visible outside of the scope.
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activate and deactivate the autoescaping from within the templates
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With both trim_blocks and lstrip_blocks enabled, you can put block tags on their own lines, and the entire block line will be removed when rendered, preserving the whitespace of the contents