py_get_item: Get/Set/Delete an item from a Python object

In reticulate: Interface to 'Python'

Get/Set/Delete an item from a Python object

Description

Access an item from a Python object, similar to how x[key] might be used in Python code to access an item indexed by key on an object x. The object's ⁠__getitem__()⁠ ⁠__setitem__()⁠ or ⁠__delitem__()⁠ method will be called.

Usage

py_get_item(x, key, silent = FALSE)

py_set_item(x, name, value)

py_del_item(x, name)

## S3 method for class 'python.builtin.object'
x[...]

## S3 replacement method for class 'python.builtin.object'
x[...] <- value

Arguments

x	A Python object.
key, name, ...	The key used for item lookup.
silent	Boolean; when TRUE, attempts to access missing items will return NULL rather than throw an error.
value	The item value to set. Assigning value of NULL calls py_del_item() and is equivalent to the python expression ⁠del x[key]⁠. To set an item value of None, you can call py_set_item() directly, or call x[key] <- py_none()

Value

For py_get_item() and [, the return value from the x.__getitem__() method. For py_set_item(), py_del_item() and ⁠[<-⁠, the mutate object x is returned.

Note

The py_get_item() always returns an unconverted python object, while [ will automatically attempt to convert the object if x was created with convert = TRUE.

Examples

## Not run: 

## get/set/del item from Python dict
x <- r_to_py(list(abc = "xyz"))

#'   # R expression    | Python expression
# -------------------- | -----------------
 x["abc"]              # x["abc"]
 x["abc"] <- "123"     # x["abc"] = "123"
 x["abc"] <- NULL      # del x["abc"]
 x["abc"] <- py_none() # x["abc"] = None

## get item from Python list
x <- r_to_py(list("a", "b", "c"))
x[0]

## slice a NumPy array
x <- np_array(array(1:64, c(4, 4, 4)))

# R expression | Python expression
# ------------ | -----------------
  x[0]         # x[0]
  x[, 0]       # x[:, 0]
  x[, , 0]     # x[:, :, 0]

  x[NA:2]      # x[:2]
  x[`:2`]      # x[:2]

  x[2:NA]      # x[2:]
  x[`2:`]      # x[2:]

  x[NA:NA:2]   # x[::2]
  x[`::2`]     # x[::2]

  x[1:3:2]     # x[1:3:2]
  x[`1:3:2`]   # x[1:3:2]


## End(Not run)

reticulate documentation built on Oct. 13, 2023, 1:08 a.m.