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PythonEmbedInR - Access a private copy of Python embedded in this R package.

This package is a modification of PythonInR which embeds a private copy of Python, isolated from any Python installation that might be on the host system. The documentation of the original package follows.

PythonInR - Makes accessing Python from within R as easy as pie.

More documentation can be found at and


R >= 2.15.0


  • pack
  • R6
  • rjson
  • methods
  • stats


install.packages("PythonEmbedInR", repos=c("", ""))
# (Use your favorite CRAN mirror above.  See for a list of available mirrors.)


Python 3

Due to api changes in Python 3 the function execfile is no longer available. The PythonInR package provides a execfile function following the typical workaround.

def execfile(filename):
    exec(compile(open(filename, 'rb').read(), filename, 'exec'), globals())

Type Casting

R to Python (pySet)

To allow a nearly one to one conversion from R to Python, PythonInR provides Python classes for vectors, matrices and data.frames which allow an easy conversion from R to Python and back. The names of the classes are PrVector, PrMatrix and PrDataFrame.

Default Conversion

R length (n) Python
logical 1 boolean
integer 1 integer
numeric 1 double
character 1 unicode
logical n > 1 PrVector
integer n > 1 PrVector
numeric n > 1 PrVector
character n > 1 PrVector
list without names n > 0 list
list with names n > 0 dict
matrix n > 0 PrMatrix
data.frame n > 0 PrDataFrame

Change the predefined conversion of pySet

PythonInR is designed in way that the conversion of types can easily be added or changed. This is done by utilizing polymorphism: if pySet is called, pySet calls pySetPoly which can be easily modified by the user. The following example shows how pySetPoly can be used to modify the behavior of pySet on the example of integer vectors.

The predefined type casting for integer vectors at an R level looks like the following:

setMethod("pySetPoly", signature(key="character", value = "integer"),
          function(key, value){
    success <- pySetSimple(key, list(vector=unname(value), names=names(value), rClass=class(value)))
    cmd <- sprintf("%s = PythonInR.prVector(%s['vector'], %s['names'], %s['rClass'])", 
                   key, key, key, key)

To change the predefined behavior one can simply use setMethod again.

pySetPoly <- PythonInR:::pySetPoly

pySet("x", 1:3)

          signature(key="character", value = "integer"),
          function(key, value){
    PythonInR:::pySetSimple(key, value)

pySet("x", 1:3)

NOTE PythonInR:::pySetSimple The functions pySetSimple and pySetPoly shouldn't be used outside the function pySet since they do not check if R is connected to Python. If R is not connected to Python this can yield to segfault !

NOTE (named lists): When executing pySet("x", list(b=3, a=2)) and pyGet("x") the order of the elements in x will change. This is not a special behavior of PythonInR but the default behavior of Python for dictionaries.

NOTE (matrix): Matrices are either transformed to an object of the class PrMatrix or to an numpy array (if the option useNumpy is set to TRUE).

NOTE (data.frame): Data frames are either transformed to an object of the class PrDataFrame or to a pandas DataFrame (if the option usePandas is set to TRUE).

R to Python (pyGet)

Python R simplify
boolean logical TRUE / FALSE
integer numeric TRUE / FALSE
double numeric TRUE / FALSE
string character TRUE / FALSE
unicode character TRUE / FALSE
bytes character TRUE / FALSE
tuple list FALSE
tuple list or vector TRUE
list list FALSE
list list or vector TRUE
dict named list FALSE
dict named list or vector TRUE
PrVetor vector TRUE / FALSE
PrMatrix matrix TRUE
PrDataFrame data.frame TRUE

Change the predefined conversion of pyGet

Similar to pySet the behavior of pyGet can be changed by utilizing pyGetPoly. The predefined version of pyGetPoly for an object of class PrMatrix looks like the following:

setMethod("pyGetPoly", signature(key="character", autoTypecast = "logical", simplify = "logical", pyClass = "PrMatrix"),
          function(key, autoTypecast, simplify, pyClass){
    x <- pyExecg(sprintf("x = %s.toDict()", key), autoTypecast = autoTypecast, simplify = simplify)[['x']]
    M <-, x[['matrix']])
    rownames(M) <- x[['rownames']]
    colnames(M) <- x[['colnames']]

For objects of type "type" no conversion is defined. Therefore, PythonInR doesn't know how to transform it into an R object so it will return a PythonInR_Object. This is kind of a nice example since the return value of type(x) is a function therefore PythonInR will return an object of type pyFunction.


One can define a new function to get elements of type "type" as follows.

pyGetPoly <- PythonInR:::pyGetPoly
setMethod("pyGetPoly", signature(key="character", autoTypecast = "logical", simplify = "logical", pyClass = "type"),
          function(key, autoTypecast, simplify, pyClass){
    pyExecg(sprintf("x = %s.__name__", key))[['x']]

NOTE pyGetPoly The functions pyGetPoly should not be used outside the function pyGet since it does not check if R is connected to Python. If R is not connected to Python this will yield to segfault !

NOTE (bytes): In short, in Python 3 the data type string was replaced by the data type bytes. More information can be found here.

Cheat Sheet

Command Short Description Example Usage
BEGIN.Python Start a Python read-eval-print loop BEGIN.Python() print("Hello" + " " + "R!") END.Python
pyAttach Attach a Python object to an R environment pyAttach("os.getcwd", .GlobalEnv)
pyCall Call a callable Python object pyCall("pow", list(2,3), namespace="math")
pyConnect Connect R to Python pyConnect()
pyDict Create a representation of a Python dict in R myNewDict = pyDict('myNewDict', list(p=2, y=9, r=1))
pyDir The Python function dir (similar to ls) pyDir()
pyExec Execute Python code pyExec('some_python_code = "executed"')
pyExecfile Execute a file (like source) pyExecfile("")
pyExecg Execute Python code and get all assigned variables pyExecg('some_python_code = "executed"')
pyExecp Execute and print Python Code pyExecp('"Hello" + " " + "R!"')
pyExit Close Python pyExit()
pyFunction Create a representation of a Python function in R pyFunction(key)
pyGet Get a Python variable pyGet('myPythonVariable')
pyGet0 Get a Python variable pyGet0('myPythonVariable')
pyHelp Python help pyHelp("help")
pyImport Import a Python module pyImport("numpy", "np")
pyIsConnected Check if R is connected to Python pyIsConnected()
pyList Create a representation of a Python list in R pyList(key)
pyObject Create a representation of a Python object in R pyObject(key)
pyOptions A function to get and set some package options pyOptions("numpyAlias", "np")
pyPrint Print a Python variable from within R pyPrint("somePythonVariable")
pySet Set a R variable in Python pySet("pi", pi)
pySource A modified BEGIN.Python aware version of source pySource("myFile.R")
pyTuple Create a representation of a Python tuple in R pyTuple(key)
pyType Get the type of a Python variable pyType("sys")
pyVersion Returns the version of Python pyVersion()

Wrapping Python packages

The following tools help generate R functions that wrap Python functions along with reference documentation (.Rd files) for the wrapper functions. The R documentation is generated from the Sphinx-based Python docstrings.


  • The Python package is downloaded and installed on the machine
  • The Python package is available on Python search path

A Python package may have multiple modules, each with its own namespace. Each module has its own functions, classes, and variables. Each function or class has its own local namespace. In R, all functions and classes within the same package share a package namespace. To avoid the namespace collisions and allow customization to the wrapping package, we provide the following functions to help you pick which modules, functions, and classes to expose in R:

  • generateRWrappers
  • generateRdFiles

The .Rd file generation must be invoked at the time the package is built, not at the time the package is loaded. The R function and constructor wrappers must be invoked at the time the package is loaded.


In this example, I will demonstrate how we generate the synapser and the synapserutils packages by wrapping the Python package synapsePythonClient.

The synapseutils module in synapsePythonClient package has the following structure:

    module: synapseutils
        module: copy
            function: copy
            function: copyWiki
            function: copyFileHandles
        module: sync
            function: syncToSynapse
            function: syncFromSynapse
        module: monitor
            function: notifyMe

Expose all functions, classes, and enums within a Python module

Generate .Rd files

To generate the R package synapserutils, our first attempt is to expose all functions under the synapseutils Python module.

In the synapserutils package, we add a configure file with the following content:


export PWD_FROM_R=${ALT_PWD-`pwd`}

# build the .Rd files
Rscript --vanilla path/to/createRdFiles.R $PWD_FROM_R

Where createRdFiles.R is an R script we add to the package, containing the code to generate the .Rd documentation files. The script invokes generateRdFiles as shown below:

args <- commandArgs(TRUE)
srcRootDir <- args[1]
                pyPkg = "synapseutils",
                container = "synapseutils")


  • srcRootDir is the path to synapserutils directory. The directory must exist prior to this call. generateRdFiles will create a folder auto-man and write the generated .Rd files in this folder.
  • pyPkg is the name of the Python package that needs to be imported, and
  • container is the name of the Python module, or class to be wrapped. This parameter can take the same value as pyPkg, a module or a class within the Python package. The value that is passed to container must be a fully qualified name.

Generate R wrappers

To generate R wrappers for Python functions and constructors, we need to add an .onLoad hook in the R package. This hook is defined in synapserutils/R/zzz.R file:

# For the R wrappers to be available in `synapserutils` package namespace,
# `setGeneric` must be defined in the `synapserutils` package. Therefore,
# we need to define it in `synapserutils` and pass it through `generateRWrappers`.
callback <- function(name, def) {
  setGeneric(name, def)
# `assign` must be call in the `synapserutils` package with the `synapserutils`
# package environment.
.NAMESPACE <- environment()
assignEnumCallback <- function(name, keys, values) {
  assign(name, setNames(values, keys), .NAMESPACE)

.onLoad <- function(libname, pkgname) {
  generateRWrappers(pyPkg = "synapseutils",
                    container = "synapseutils",
                    setGenericCallback = callback,
                    assignEnumCallback = assignEnumCallback)

The values for pyPkg and container parameters to generateRWrappers() must match those parameters passed to generateRdFiles() so that the reference doc's match the generated R functions.

For more information about how to use setGeneric, please view its reference documentation by:


Expose a subset of functions within a Python module

For many reasons, some Python functions are meant to be used internally, and these do not need to be exposed in the R package. For example, notifyMe is a Python decorator, and can only be used for other Python functions.

Let's omit the following functions from synapseutils module:

  • copyFileHandles
  • notifyMe

We need to specify a function like selectFunctions below in shared.R, an .R script that can be accessed by both zzz.R and createRdFiles.R:

toOmit <- c("copyFileHandles", "notifyMe")
selectFunctions <- function(x) {
    if (any(x$name == toOmit)) {

Then from the R script that generates .Rd files, createRdFiles.R, we update generateRdFiles as follows:

                pyPkg = "synapseutils",
                container = "synapseutils",
                functionFilter = selectFunctions)

And from zzz.R, update generateRWrappers to maintain consistency as follows:

generateRWrappers(pyPkg = "synapseutils",
                  container = "synapseutils",
                  setGenericCallback = callback,
                  assignEnumCallback = assignEnumCallback,
                  functionFilter = selectFunctions)

Expose a subset of classes within a Python module

The synapseclient module in the synapsePythonClient has the following structure:

    module: synapseclient
        module: client
            class: Synapse
                function: get
                function: login
        module: entity
            class: Entity
                function: get
                function: privateGet
            class: File
                function: get
                function: privateGet
            class: Folder
                function: get
                function: privateGet

Now let's try a more complicated example where we want to expose the following functions and classes from the synapseclient.entity module:

  class: File
      function: get
  class: Folder
      function: get

Note that we do not want the following from the synapseclient.entity module:

  • function: privateGet from any of the classes, and
  • class: Entity

First, we define the selectClasses function in the shared.R file:

methodsToOmit <- "privateGet"
classToSkip <- "Entity"
selectClasses <- function(class) {
    if (any(class$name == classToSkip)) {
    if (!is.null(class$methods)) {
        culledMethods <- lapply(X = class$methods, function(x) {
            if (any(x$name == methodsToOmit)) NULL else x;
        # Now remove the nulls
        nullIndices <- sapply(culledMethods, is.null)
        if (any(nullIndices)) {
            class$methods <- culledMethods[-which(nullIndices)]

Then we call generateRdFiles and generateRWrappers as follows:

                pyPkg = "synapseclient",
                container = "synapseclient.entity",
                classFilter = selectClasses)
generateRWrappers(pyPkg = "synapseclient",
                  container = "synapseclient.entity",
                  setGenericCallback = callback,
                  assignEnumCallback = assignEnumCallback,
                  classFilter = selectClasses)

Expose functions within a singleton object

In some cases, we want to expose a set of Python functions which are an object's methods, but without exposing the object itself. For example, in the synapser package we wish to make available the methods in synapseclient.client.Synapse without requiring the R user to instantiate the Synapse object. The following will create a singleton object at package load time and expose the object's methods to be called directly.

In a Python session, we would do the following:

  syn = synapseclient.Synapse()

And in R, users would not need to know about the Synapse object:


Note that:

  • All function calls in R access a common underlying Python object Synapse
  • In the following example, the function names in R will be prepended with a syn prefix.

For generated .Rd files, we use functionPrefix parameter as follows:

                pyPkg = "synapseclient",
                container = "synapseclient.client.Synapse",
                functionPrefix = "syn")

To generate the R wrappers, we need to instantiate the Python object in zzz.R file. Then we pass the object name to generateRWrapper via pySingletonName parameter.

.onLoad <- function(libname, pkgname) {
  pyExec("synapse = synapseclient.Synapse()")

  generateRWrappers(pyPkg = "synapseclient",
                    container = "synapseclient.client.Synapse",
                    setGenericCallback = callback,
                    assignEnumCallback = assignEnumCallback,
                    pySingletonName = "synapse",
                    functionPrefix = "syn")

Override the returned object in R

You may wish to intercept and modify the values returned by the auto-generated R functions. In the following example we wish to intercept certain returned R6 objects and modify their class names.

objectDefinitionHelper <- function(object) {
  # change returned object name from "GeneratorWrapper.<some function name>" to "GeneratorWrapper"
  if (grepl("^GeneratorWrapper", class(object)[1])) {
    class(object)[1] <- "GeneratorWrapper"

generateRWrappers(pyPkg = "synapseclient",
                  container = "synapseclient.client.Synapse",
                  setGenericCallback = callback,
                  assignEnumCallback = assignEnumCallback,
                  transformReturnObject = objectDefinitionHelper)

Note: transformReturnObject will be applied to the returned values from all generated functions. The transformation cannot depend on the function which generated the returned value.

Notes on generateRdFiles

This function converts Python docstrings into .Rd files, recognizing a subset of Sphinx tags:

  • :parameter:
  • :param:
  • :type:
  • :var:
  • :return(s):
  • :func:
  • :meth:
  • :example(s):
  • :Example(s):
  • :py:class:
  • :py:mod:
  • :py:func:
  • :py:meth:

Usage Examples

Dynamic Documents

Data and Text Mining


Based off of PythonInR ( but includes a standalone, compiled from source python instead of relying on the python installed on the host machine






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