Some Python libraries output the result of their functions to STDOUT - and in a Python UDF in Snowflake I need to capture that value to a String to return it.
For example the output of help()
or numpy.show_config()
.
You can capture stdout using contextlib.redirect_stdout
.
For example, to capture the output of help(numpy)
:
create or replace function help_numpy()
returns string
language python
runtime_version = '3.8'
packages = ('numpy')
handler = 'x'
as $$
import io
from contextlib import redirect_stdout
from pydoc import help
import numpy
def x():
f = io.StringIO()
with redirect_stdout(f):
help(numpy)
return f.getvalue()
$$;
select help_numpy();
Or to capture the output of numpy.show_config()
you just need to replace the functions called inside the redirect_stdout()
block:
with redirect_stdout(f):
numpy.show_config()
Note that to use help()
we also had to from pydoc import help
. Otherwise you'll get the error NameError: name 'help' is not defined in function HELP with handler
.
That's a great idea for all UDF languages. Open source JavaScript is often filled with with alert
, window.alert
, console.log
etc. To capture the alert and console out functions in JavaScript:
create or replace function STDOUT()
returns array
language javascript
as
$$
//----- Start of standard out intercepts. Add to top of UDF
console.logs = [];
window = {};
console.log = function(){ console.logs.push({"type":"log", "timestamp":new Date().toISOString(), "out":Array.from(arguments)}) };
console.warn = function(){ console.logs.push({"type":"warn", "timestamp":new Date().toISOString(), "out":Array.from(arguments)}) };
console.error = function(){ console.logs.push({"type":"error", "timestamp":new Date().toISOString(), "out":Array.from(arguments)}) };
console.debug = function(){ console.logs.push({"type":"debug", "timestamp":new Date().toISOString(), "out":Array.from(arguments)}) };
alert = function(){ console.logs.push({"type":"alert", "timestamp":new Date().toISOString(), "out":Array.from(arguments)}) };
window.alert = function(){ console.logs.push({"type":"alert", "timestamp":new Date().toISOString(), "out":Array.from(arguments)}) };
//----- End of standard out intercepts
console.log("My log.");
console.warn("My warning");
console.error("My error");
alert("My alert");
window.alert("My window alert");
return console.logs;
$$;
select STDOUT();
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