Is it possible to get output of pydot graph without intermediate file?

Question

I have a very simple graph that I want to plot as svg. For example:

# graph.dot
graph { 
        a -- b; 
        b -- c; 
    } 

I am currently using pydot to read the file and then generate the svg file as follows:

import pydot
graphs = pydot.graph_from_dot_file('graph.dot')
graphs[0].write_svg('graph.svg') # there is only 1 graph so the 0 index.

However, I need to do this without the need of intermediate files graph.dot and graph.svg. I have the code content of graph.dot in a string, corresponding to which I need the svg output in string.

I need something like:

graph_dot = "... ..." # string, I have this
graph_svg = convert_dot_to_svg(graph_dot) 
# i need something like convert_dot_to_svg()

My question is not limited to pydot only. If anyone knows a web api using which I can do this, then also it will do.

Thanks a Lot, in advance.

Catarinacatarrh

I've never used pydot (but I do know Graphviz), but a quick look at the pydot docs suggests that you can use a file-like object instead of a file. So you should try StringIO or BytesIO from the standard io module. – Roentgenotherapy

@PM2Ring you are right that I can use io to take input. But how to replace the write_svg function? – Catarinacatarrh

@PM2Ring As mentioned, question isn't limited to pydot itself. Can you tell me a way to get the svg string corresponding to dot string in Graphviz. Any way is fine. – Catarinacatarrh

If .write_svg accepts an open file handle instead of a file name, then it will "just work" if you supply it a StringIO or BytesIO object. If you've never used the io module before, I suggest you study the docs & do a few experiments; it's a very useful module. – Roentgenotherapy

Ok cool ... Thanks :) – Catarinacatarrh

Sorry, I don't have any specifc advice about DOT -> SVG conversion; I normally use the Graphviz command line programs to convert a DOT file to SVG. – Roentgenotherapy

No problem, and thanks a lot for your time and valuable comments. Finally, solution could be figured out. I have posted the answer on what worked. – Catarinacatarrh

Answer 1

After spending some more time looking at the available methods on pydot object and graph object, it could be figured out:

The following code works:

import pydot    
dot_string = """graph { 
                    a -- b; 
                    b -- c; 
                } """

graphs = pydot.graph_from_dot_data( dot_string )
svg_string = graphs[0].create_svg() 

Catarinacatarrh

FWIW, pydot still needs graphviz to be installed. Quoted from this blog post: "If we look at the Pydot Pypi page you can see already a hint on this as it will tell you the following; Pydot is an interface to Graphviz and can parse and dump into the DOT language used by Grapgiz. Pydot is written in pure Python." – Valse

now what do you do with svg_string? – Aara