Querying¶
As you have seen in the previous section, you can navigate into RedBaron tree
only using attribute access and index access on list of nodes with the use of
the .help()
method to know what you can do. However, RedBaron offers
way more powerful and convenient tools to do that.
.find()¶
To retrieve a single node, you can use the .find()
method by passing it
one of the identifiers listed in .help()
of node you want to get, this way:
In [1]: red = RedBaron("a = 1")
In [2]: red.help()
0 -----------------------------------------------------
AssignmentNode()
# identifiers: assign, assignment, assignment_, assignmentnode
operator=''
target ->
NameNode()
# identifiers: name, name_, namenode
value='a'
annotation ->
None
value ->
IntNode()
# identifiers: int, int_, intnode
value='1'
In [3]: red.find('NameNode').help()
NameNode()
# identifiers: name, name_, namenode
value='a'
In [4]: red.find('namenode').help() # identifiers are not case sensitive
NameNode()
# identifiers: name, name_, namenode
value='a'
In [5]: red.find('name')
Out[5]: a
This will recursively travel the tree and return the first node of that type.
You can also specify attributes of the node that you want to match:
In [6]: red = RedBaron("a = b")
In [7]: red.find('name').help()
NameNode()
# identifiers: name, name_, namenode
value='a'
In [8]: red.find('name', value='b').help()
NameNode()
# identifiers: name, name_, namenode
value='b'
If you don’t want a recursive approach but only on the first level on the current node or node list, you can pass recursive=False
to .find()
.
Like BeautifulSoup, RedBaron provides a shorthand to .find()
, you can
write the name of the target as an attribute of the node and this will do a .find()
in the same fashion:
In [9]: red = RedBaron("a = b")
In [10]: red.find('name')
Out[10]: a
In [11]: red.name
Out[11]: a
You might have noticed that some identifiers end with a _
, those are
for the case where the identifier might be a Python reserved keyword like
if
, or while
for example.
Be aware that if you do a red.something_that_can_be_a_node_identifier
and this is also not an attribute of a node, this will raise an
AttributeError
.
.find_all()¶
.find_all()
is extremely similar to .find()
except it returns a
node list containing all the matching queries instead of a single one. Like in
BeautifulSoup, __call__
is aliased to find_all
(meaning that if
you try to call the node this way node(some_arguments)
this will call
.find_all()
with the arguments).
In [12]: red = RedBaron("a = b")
In [13]: red.find_all("NameNode")
Out[13]:
0 a
1 b
In [14]: red.find_all("name")
Out[14]:
0 a
1 b
In [15]: red.findAll("name")
Out[15]:
0 a
1 b
In [16]: red.findAll("name", value="b")
Out[16]: 0 b
In [17]: red("name", value="b")
Out[17]: 0 b
.find_all()
also supports the option recursive=False
.
Advanced querying¶
.find()
and .find_all()
offer more powerful comparison mean
than just equality comparison.
Callable (lambda)¶
Instead of passing a string to test properties of the identifier of a node, you can pass a callable, like a lambda. It will receive the value as first argument:
In [18]: red = RedBaron("a = [1, 2, 3, 4]")
In [19]: red.find("int", value=lambda value: int(value) % 2 == 0)
Out[19]: 2
In [20]: red.find_all("int", value=lambda value: int(value) % 2 == 0)
Out[20]:
0 2
1 4
In [21]: red.find(lambda identifier: identifier == "comma")
Out[21]: ,
In [22]: red.find_all(lambda identifier: identifier == "comma")
Out[22]:
0 ,
1 ,
2 ,
Regex¶
Instead of passing a string to test properties of a node, you can pass a compiled regex:
In [23]: import re
In [24]: red = RedBaron("abcd = plop + pouf")
In [25]: red.find("name", value=re.compile("^p"))
Out[25]: plop
In [26]: red.find_all("name", value=re.compile("^p"))
Out[26]:
0 plop
1 pouf
In [27]: red.find(re.compile("^n"))
Out[27]: abcd
In [28]: red.find_all(re.compile("^n"))
Out[28]:
0 abcd
1 plop
2 pouf
Having to compile regex is boring, so you can use this shorthand syntax instead (prefixing a string with “re:”):
In [29]: red = RedBaron("abcd = plop + pouf")
In [30]: red.find("name", value="re:^p")
Out[30]: plop
In [31]: red.find_all("name", value="re:^p")
Out[31]:
0 plop
1 pouf
In [32]: red.find("re:^n")
Out[32]: abcd
In [33]: red.find_all("re:^n")
Out[33]:
0 abcd
1 plop
2 pouf
Globs¶
Same than in a shell, you can use globs by prefixing the string with “g:”:
In [34]: red = RedBaron("abcd = plop + pouf")
In [35]: red.find("name", value="g:p*")
Out[35]: plop
In [36]: red.find_all("name", value="g:p*")
Out[36]:
0 plop
1 pouf
In [37]: red.find("g:n*")
Out[37]: abcd
In [38]: red.find_all("g:n*")
Out[38]:
0 abcd
1 plop
2 pouf
In the background, the comparison is done using the fnmatch module of the standard lib.
List or tuple¶
You can pass a list as a shorthand to test if the tested attribute is in any of the member of the list/tuple:
In [39]: red = RedBaron("foo\nbar\nbaz")
In [40]: red.find("name", value=["foo", "baz"])
Out[40]: foo
In [41]: red.find("name", value=("foo", "baz"))
Out[41]: foo
In [42]: red("name", value=["foo", "baz"])
Out[42]:
0 foo
1 baz
In [43]: red("name", value=("foo", "baz"))
Out[43]:
0 foo
1 baz
In [44]: red = RedBaron("1\nstuff\n'string'\n")
In [45]: red.find(["int", "string"])
Out[45]: 1
In [46]: red(["int", "string"])
Out[46]:
0 1
1 'string'
*args and default value¶
You can also pass as many callable as args (without giving it a key) as you want, those callables will receive the node itself as first argument (and must return a value that will be tested as a boolable):
In [47]: red = RedBaron("a = [1, 2, 3, 4]")
In [48]: red.find("int", lambda node: int(node.value) % 2 == 0)
Out[48]: 2
In [49]: red.find_all("int", lambda node: int(node.value) % 2 == 0)
Out[49]:
0 2
1 4
In [50]: red.find("int", lambda node: int(node.value) % 2 == 0, lambda node: int(node.value) == 4)
Out[50]: 4
To ease the usage of RedBaron in ipython (and in general), you can pass any of
the previous testing methods (except the lambda) as the first argument of
*args, it will be tested against the default testing attribute which is the
“value” attribute by default. This mean that: red.find("name", "foo")
is the equivalent of red.find("name", value="foo")
.
If the default tested attribute is different, it will be shown in
.help()
. For now, the 2 only cases where this happens is on class node
and funcdef node where the attribute is “name”.
In [51]: red = RedBaron("foo\ndef bar(): pass\nbaz\ndef badger(): pass")
In [52]: red.find("name", "baz")
Out[52]: baz
In [53]: red.find("def", "bar")
Out[53]: def bar(): pass
In [54]: red.find("def").help()
DefNode()
# identifiers: def, def_, defnode, funcdef, funcdef_
# default test value: name
async=False
name='bar'
return_annotation ->
None
decorators ->
arguments ->
value ->
* PassNode()
# identifiers: pass, pass_, passnode