Rename add_variable to set_variable and explain it in more detail

docs/source/changelog.rst

@@ -43,10 +43,11 @@ Added
   list of options for the geometry package), ``document_options`` (a list of
   options to place in the document class), ``indents`` (an option to select
   whether the documents elements are indented), ``page_numbers`` (an option to
-  choose whether to use the lastpage package or not), ``font_size`` (the font
-  size to set at the beggining of the document).
+  choose whether to use page numbers or not), ``font_size`` (the font size to
+  set at the beggining of the document).
 - Added several new methods to the `.Document`: ``change_page_style``,
-  ``change_document_style``, ``add_color``, ``change_length``.
+  ``change_document_style``, ``add_color``, ``change_length``,
+  ``set_variable``.
 - Added a new `.position` package with the following classes: `.Center` (an
   environment with centered content), `.FlushLeft` (an environment with left
   aligned content), `.FlushRight` (an environment with right aligned content),

pylatex/document.py

@@ -340,8 +340,12 @@ def change_length(self, parameter, value):
         self.preamble.append(UnsafeCommand('setlength',
                                            arguments=[parameter, value]))
 
-    def add_variable(self, name, value):
-        """Add a variable which can be used inside the document.
+    def set_variable(self, name, value):
+        r"""Add a variable which can be used inside the document.
+
+        Variables are defined before the preamble. If a variable with that name
+        has already been set, the new value will override it for future uses.
+        This is done by appending ``\renewcommand`` to the document.
 
         Args
         ----

tests/args.py

@@ -54,7 +54,8 @@ def test_document():
     doc.change_document_style(style="plain")
     doc.add_color(name="lightgray", model="gray", description="0.6")
     doc.add_color(name="abitless", model="gray", description="0.8")
-    doc.add_variable(name="myVar", value="1234")
+    doc.set_variable(name="myVar", value="1234")
+    doc.set_variable(name="myVar", value="1234")
     doc.change_length(parameter=r"\headheight", value="0.5in")
 
     doc.generate_tex(filepath='')