modal.io_streams

modal.io_streams.StreamReader

class StreamReader(typing.Generic)

Retrieve logs from a stream (stdout or stderr).

As an asynchronous iterable, the object supports the for and async for statements. Just loop over the object to read in chunks.

Usage

from modal import Sandbox

sandbox = Sandbox.create(
    "bash",
    "-c",
    "for i in $(seq 1 10); do echo foo; sleep 0.1; done",
    app=app,
)
for message in sandbox.stdout:
    print(f"Message: {message}")

file_descriptor

@property
def file_descriptor(self) -> int:

Possible values are 1 for stdout and 2 for stderr.

read

def read(self) -> T:

Fetch the entire contents of the stream until EOF.

Usage

from modal import Sandbox

sandbox = Sandbox.create("echo", "hello", app=app)
sandbox.wait()

print(sandbox.stdout.read())

modal.io_streams.StreamWriter

class StreamWriter(object)

Provides an interface to buffer and write logs to a sandbox or container process stream (stdin).

write

def write(self, data: Union[bytes, bytearray, memoryview, str]) -> None:

Write data to the stream but does not send it immediately.

This is non-blocking and queues the data to an internal buffer. Must be used along with the drain() method, which flushes the buffer.

Usage

from modal import Sandbox

sandbox = Sandbox.create(
    "bash",
    "-c",
    "while read line; do echo $line; done",
    app=app,
)
sandbox.stdin.write(b"foo\n")
sandbox.stdin.write(b"bar\n")
sandbox.stdin.write_eof()

sandbox.stdin.drain()
sandbox.wait()

write_eof

def write_eof(self) -> None:

Close the write end of the stream after the buffered data is drained.

If the process was blocked on input, it will become unblocked after write_eof(). This method needs to be used along with the drain() method, which flushes the EOF to the process.

drain

def drain(self) -> None:

Flush the write buffer and send data to the running process.

This is a flow control method that blocks until data is sent. It returns when it is appropriate to continue writing data to the stream.

Usage

writer.write(data)
writer.drain()

Async usage:

writer.write(data)  # not a blocking operation
await writer.drain.aio()