BaseLoader Class

Inheritance diagram of BaseLoader

class BaseLoader

Baseclass for all loaders. Subclass this and override get_source to implement a custom loading mechanism. The environment provides a get_template method that calls the loader’s load method to get the Template object.

A very basic example for a loader that looks up templates on the file system could look like this:

from jinja2 import BaseLoader, TemplateNotFound
from os.path import join, exists, getmtime

class MyLoader(BaseLoader):

    def __init__(self, path):
        self.path = path

    def get_source(self, environment, template):
        path = join(self.path, template)
        if not exists(path):
            raise TemplateNotFound(template)
        mtime = getmtime(path)
        with file(path) as f:
            source ='utf-8')
        return source, path, lambda: mtime == getmtime(path)


get_source(environment, template) Get the template source, filename and reload helper for a template.
list_templates() Iterates over all templates.
load(environment, name[, globals]) Loads a template.


has_source_access bool(x) -> bool


class BaseLoader

Method details

get_source(environment, template)

Get the template source, filename and reload helper for a template. It’s passed the environment and template name and has to return a tuple in the form (source, filename, uptodate) or raise a TemplateNotFound error if it can’t locate the template.

The source part of the returned tuple must be the source of the template as unicode string or a ASCII bytestring. The filename should be the name of the file on the filesystem if it was loaded from there, otherwise None. The filename is used by python for the tracebacks if no loader extension is used.

The last item in the tuple is the uptodate function. If auto reloading is enabled it’s always called to check if the template changed. No arguments are passed so the function must store the old state somewhere (for example in a closure). If it returns False the template will be reloaded.


Iterates over all templates. If the loader does not support that it should raise a TypeError which is the default behavior.

load(environment, name, globals=None)

Loads a template. This method looks up the template in the cache or loads one by calling get_source(). Subclasses should not override this method as loaders working on collections of other loaders (such as PrefixLoader or ChoiceLoader) will not call this method but get_source directly.

Attribute details

has_source_access = True

if set to False it indicates that the loader cannot provide access to the source of templates.

New in version 2.4.

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