pycallflow 0.2.0

Maps function, class, and method calls in python projects, modules, and files

pycallflow

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WARNING

Do not use pycallflow to map hostile or potentially malicious python code. Code may be executed as it is examined.

What is Pycallflow

Pycallflow produces GraphViz-compatible output that visually shows the flow of calls within a module, package, or directory of python files like this:

I wrote it to help me get a grip on python projects that have accreted files and capability over time. It was difficult to hand trace the call flows when there were problems and upgrades to be done.

There are limitations and some significant warnings. Please see Warnings below

What it does

Pycallflow recursively imports and analyzes the files in a module or directory to identify all of the declared code entities (functions, methods, and classes). It maps the calls between these entities to produce a network graph which is then rendered in DOT language.

Installation

pip install pycallflow

Usage

Basics

Invoke with

python -m pycallflow [target]

To generate a DOT-language call flow diagram of every discovered entity.

If you have GraphViz installed you can pipe it:

python -m pycallflow [target] | dot -Tpng -ofilename.png

Flow Arrows (edges)

The colors of the edges do not mean anything. I rotate through a list of contrasting colors in an attempt make it easier to trace the flow lines. You can set the color with ---edge_color if you want it fixed to a specifc color.

You may see dashed edges. Dashed edges indicate the call or reference may be ambiguous. This means there are multiple entities with the exact same name (i.e. two or more files or classes contain a function with the same name). This is very common with subclasses that override parent methods. Though Python always seems to know which one you mean, it's a little harder to figure out from the outside. Improving this is a main goal for the future.

Clean up

The diagrams can get quite busy, but there are options that can limit some of the noise.

--clean

Specifying this option will turn all of the clean up options on. I recommend it under most circumstances.

--suppress_recursive_calls

Entities that recurse on themselves will get loop indicators like this:

python -m pycallflow --suppress_recursive_calls [target]

Will result in the elimination of these loops:

--combine_calls

Entities may call the same entity more than once. By default, this will show as multiple indicators:

python -m pycallflow --combine_calls [target]

Will allow only one indicator between entities:

--suppress_class_references

By default an entity that references a class will get an indicator similar to :

This can be handy if an entity assigns a class reference to a variable. However, it may be obvious that the entity is calling a class method in which case the "reference" indicator will just be added noise.

python -m pycallflow --suppress_class_references [target]

Will clean these up:

--suppress_calls_to_init

Typically the only thing calling __init__() is a subclass calling super().__init__(). This can add unnecessary complexity to the diagram without adding value. Specify --suppress_calls_to_init to eliminate these.

--match_to_file

This is an option to limit ambiguous calls (calls to an entity that shares a name across the analyzed code space). When this is set, pycallflow will look for entities first in the same file as the calling entity and will choose those over other files.

Investigate Specific Entities

You may only be interested in the call flow upstream and downstream of a specific entity (or entities). The --select_entity_id option allows you to focus your attention. Here is the workflow.

Get a list of discovered entities

Use:

python -m pycallflow -o entity_list [target]

To get a numbered list of discovered entities. For example, running this against pycallflow will give this:

>python -m pycallflow -o entity_list pycallflow
|   entityID | name                                  | Type     | import path                        |
|------------|---------------------------------------|----------|------------------------------------|
|          1 | addCallDBEntry                        | function | pycallflow.analyzeCallFlow         |
|          2 | buildCallflowDB                       | function | pycallflow.analyzeCallFlow         |
|          3 | entitylists                           | function | pycallflow.analyzeCallFlow         |
|          4 | findAllEntityIDWithName               | function | pycallflow.analyzeCallFlow         |
|          5 | addEntityToDB                         | function | pycallflow.buildDeclaredEntitiesDB |
|          6 | buildDeclaredEntitiesDB               | function | pycallflow.buildDeclaredEntitiesDB |
|          7 | findDeclaredEntities                  | function | pycallflow.buildDeclaredEntitiesDB |
|          8 | findDeclaredEntities_inlineSave       | function | pycallflow.buildDeclaredEntitiesDB |
|          9 | inspectAndSaveEntities                | function | pycallflow.buildDeclaredEntitiesDB |
|         10 | inspectEntity                         | function | pycallflow.buildDeclaredEntitiesDB |
|         11 | addFileToDB                           | function | pycallflow.buildFileDB             |
|         12 | buildFileDB                           | function | pycallflow.buildFileDB             |
|         13 | getFileList                           | function | pycallflow.buildFileDB             |
|         14 | cli_run                               | function | pycallflow.callflow                |
|         15 | collectData                           | function | pycallflow.callflow                |
|         16 | callFlowData                          | class    | pycallflow.callFlowData            |
|         17 | __init__                              | function | pycallflow.callFlowData            |
|         18 | addDiscoveredObject                   | function | pycallflow.callFlowData            |
--- SNIP --- 

The entityID will remain constant between runs provided no new files, functions, classes, or methods are introduced. If you add new code, just run the -o entity_list again.

Select your entityID

Just use --select_entity_id id1,id2,.. similar to:

python -m pycallflow --select_entity_id 5,11 pycallflow

Resulting in:

Analyzing Directories

The code you want to examine may not be package or module, but just code files in a directory or layered directories. Use the --directory option to make pycallflow consider your target a directory and not a module.

Warnings and Limitations

Analyzed Code WILL Execute

Pycallflow works by importing files and then inspecting the objects that result. This can only be done by actually executing the code. If there is code not protected by a if __name__ == "__main__": clause or buried inside a class, method, or function it WILL EXECUTE.

If the executed code contains a sys.exit() or other process termination, pycallflow will not produce any output. I learned this from experience.

To prevent corrupting the DOT output, stdout is redirected to os.devnull (you can specify a file with --stdout_capture_file). This won't prevent other operations from happening.

DO NOT USE THIS ON HOSTILE OR MALICIOUS CODE

Only entities in the target files are analyzed

Supporting packages and libraries are not examined.

Currently can't analyze installed libraries or packages

Right now you can't specify a system package (like requests) and have it run. I just haven't put that in place yet. However, you could clone any repository and then run pycallflow on that.

License

pycallflow is distributed under the terms of the MIT license.