Stata Python

Stata supports calling out to an embedded Python interpretter.

Contents

Stata Python

Installation

To list recognized Python environments, try python search. If an valid environment is known to exist but was not recognized, try:

python set exec "C:\path\to\python\installation"

To manipulate (i.e., append or prepend) the PYTHONPATH environment variable, try:

python set userpath "C:\foo" "C:\bar" "C:\baz"
python set userpath "C:\foo" "C:\bar" "C:\baz", prepend

To make these settings permanent, add the permanent option.

Usage

Much like Mata, there is a Python scope.

python: print("Hello, world")

Subsessions

Within an interactive Stata session, enter a Python interactive subsession with the -python- command.

. // This is an interactive Stata session
. local int_var = 3

. local str_var = "This is a Stata string"

.
. // Now start the Python subsession
. python
---------------------------------------- python (type end to exit) -----------
>>>
>>> myint = 3
>>> mystr = "This is a Python string
>>>
>>> # Stata macros evaluate here
>>> `int_var'
3
>>> "`str_var'".split(" ")
['This', 'is', 'a', 'Stata', 'string']
>>>
>>> # Call back out to the Stata session
>>> stata: webuse auto, clear

Programs

Within an ado file, run Python code like:

python:
import sqlite3
import pandas as pd

con = sqlite3.connect("`a'")
df = pd.read_sql_query("SELECT * from `b'", con)
con.close()
end

Note that objects in the __main__ namespace are retained across Python sessions. If the con sqlite3.Connection object was not closed, it would have remained in memory until the Stata process ended.

Best practices for bundling Python in an ado file are:

Write as a function to be called, not as a script that evaluates immediately
Write an accompanying Stata program to wrap it, and handle everything user-facing there
Call the function from a scope

program varsum
    version 16.0
    syntax varname [if] [in]

    python: _varsum("`varlist'", "`touse'")
    display as txt " sum of ‘varlist’: " as res r(sum)
end

python:
from sfi import Data, Scalar
def _varsum(varname, touse):
    x = Data.get(varname, None, touse)
    Scalar.setValue("r(sum)", sum(x))
end

. webuse auto
(1978 Automobile Data)

. varsum price
sum of price: 456229

. varsum price if foreign
sum of price: 140463

Stata Interoperability

To move data between Python and Stata processes, use the sfi module.

python:

import pandas as pd
from sfi import Data

# initialize N cases
Data.setObsTotal(len(df))

# initialize variables
Data.addVarDouble("id")
Data.addVarStr("name",5)

# copy columnar data
Data.store("id", None, df["id"], None)
Data.store("zipcode", None, df["name"], None)

# free memory
del df

end

This module can be imported into both programs and interactive sessions. It is not a publicly available module.

Stata/Python