custom_scaffold_py_function_wrapper: Custom Scaffolding of R Wrappers for Python Functions

In scaffolder: Scaffolding Interfaces to Packages in Other Programming Languages

Description

This function can be used to generate R wrapper for a specified Python function while allowing to inject custom code for critical parts of the wrapper generation, such as process the any part of the docs obtained from py_function_docs() and append additional roxygen fields. The result from execution of python_function is assigned to a variable called python_function_result that can also be processed by postprocess_fn before writing the closing curly braces for the generated wrapper function.

Usage

custom_scaffold_py_function_wrapper(
  python_function,
  r_function = NULL,
  additional_roxygen_fields = NULL,
  process_docs_fn = function(docs) docs,
  process_param_fn = function(param, docs) param,
  process_param_doc_fn = function(param_doc, docs) param_doc,
  postprocess_fn = NULL,
  file_name = NULL
)

Arguments

python_function	Fully qualified name of Python function or class constructor (e.g. tf$nn$top_k)
r_function	Name of R function to generate (defaults to name of Python function if not specified)
additional_roxygen_fields	A list of additional roxygen fields to write to the roxygen docs, e.g. list(export = "", rdname = "generated-wrappers").
process_docs_fn	A function to process docs obtained from reticulate::py_function_docs(python_function).
process_param_fn	A function to process each parameter needed for python_funcion before executing python_funcion.
process_param_doc_fn	A function to process the roxygen docstring for each parameter.
postprocess_fn	A function to inject any custom code in the form of a string before writing the closing curly braces for the generated wrapper function.
file_name	The file name to write the generated wrapper function to. If NULL, the generated wrapper will only be printed out in the console.

Examples

library(tensorflow)
library(stringr)

# Example of a `process_param_fn` to cast parameters with default values
# that contains "L" to integers
process_int_param_fn <- function(param, docs) {
  # Extract the list of parameters that have integer values as default
  int_params <- gsub(
    " = [-]?[0-9]+L",
    "",
    str_extract_all(docs$signature, "[A-z]+ = [-]?[0-9]+L")[[1]])
  # Explicitly cast parameter in the list obtained above to integer
  if (param %in% int_params) {
    param <- paste0("as.integer(", param, ")")
  }
  param
}

# Note that since the default value of parameter `k` is `1L`. It is wrapped
# by `as.integer()` to ensure it's casted to integer before sending it to `tf$nn$top_k`
# for execution. We then print out the python function result.
custom_scaffold_py_function_wrapper(
  "tf$nn$top_k",
  r_function = "top_k",
  process_param_fn = process_int_param_fn,
  postprocess_fn = function() { "print(python_function_result)" })

scaffolder documentation built on March 20, 2020, 5:07 p.m.