diff --git a/returnn/datasets/sprint.py b/returnn/datasets/sprint.py
index 475a094234..0d46f5279e 100644
--- a/returnn/datasets/sprint.py
+++ b/returnn/datasets/sprint.py
@@ -23,8 +23,9 @@
 from returnn.datasets.basic import Dataset, DatasetSeq
 from .cached2 import CachedDataset2
 from returnn.log import log
-from returnn.util.task_system import Unpickler, numpy_copy_and_set_unused
-from returnn.util.basic import eval_shell_str, interrupt_main, unicode, PY3, BytesIO, close_all_fds_except
+from returnn.util.task_system import numpy_copy_and_set_unused
+from returnn.util.basic import eval_shell_str, interrupt_main, unicode, PY3, close_all_fds_except
+import returnn.util.basic as util
 
 
 class SprintDatasetBase(Dataset):
@@ -913,31 +914,9 @@ def _read_next_raw(self):
         :return: (data_type, args)
         :rtype: (str, object)
         """
-        import struct
-
-        size_raw = self.pipe_c2p[0].read(4)
-        if len(size_raw) < 4:
-            raise EOFError
-        (size,) = struct.unpack("<i", size_raw)
-        assert size > 0, "%s: We expect to get some non-empty package. Invalid Python mod in Sprint?" % (self,)
-        stream = BytesIO()
-        read_size = 0
-        while read_size < size:
-            data_raw = self.pipe_c2p[0].read(size - read_size)
-            if len(data_raw) == 0:
-                raise EOFError("%s: expected to read %i bytes but got EOF after %i bytes" % (self, size, read_size))
-            read_size += len(data_raw)
-            stream.write(data_raw)
-        stream.seek(0)
-        try:
-            if PY3:
-                # encoding is for converting Python2 strings to Python3.
-                # Cannot use utf8 because Numpy will also encode the data as strings and there we need it as bytes.
-                data_type, args = Unpickler(stream, encoding="bytes").load()
-            else:
-                data_type, args = Unpickler(stream).load()
-        except EOFError:
-            raise Exception("%s: parse error of %i bytes (%r)" % (self, size, stream.getvalue()))
+        # encoding is for converting Python2 strings to Python3.
+        # Cannot use utf8 because Numpy will also encode the data as strings and there we need it as bytes.
+        data_type, args = util.read_pickled_object(self.pipe_c2p[0], encoding="bytes")
         return data_type, args
 
     def _join_child(self, wait=True, expected_exit_status=None):
diff --git a/returnn/sprint/control.py b/returnn/sprint/control.py
index a3bd447dd2..3a4f43779f 100644
--- a/returnn/sprint/control.py
+++ b/returnn/sprint/control.py
@@ -15,15 +15,14 @@
 import os
 import numpy
 import typing
-import io
-import struct
 from threading import Condition
 
 import returnn.__main__ as rnn
 import returnn.util.task_system as task_system
 import returnn.util.debug as debug
-from returnn.util.task_system import Pickler, Unpickler, numpy_set_unused
+from returnn.util.task_system import numpy_set_unused
 from returnn.util.basic import to_bool, long
+import returnn.util.basic as util
 
 InitTypes = set()
 Verbose = False  # disables all per-segment log messages
@@ -434,31 +433,10 @@ def _get_loss_and_error_signal_via_sprint_callback(self, seg_name, orthography,
         return loss, error_signal
 
     def _send(self, data):
-        stream = io.BytesIO()
-        Pickler(stream).dump(data)
-        raw_data = stream.getvalue()
-        assert len(raw_data) > 0
-        self.pipe_c2p.write(struct.pack("<i", len(raw_data)))
-        self.pipe_c2p.write(raw_data)
-        self.pipe_c2p.flush()
+        util.write_pickled_object(self.pipe_c2p, data)
 
     def _read(self):
-        p = self.pipe_p2c
-        size_raw = p.read(4)
-        if len(size_raw) < 4:
-            raise EOFError
-        (size,) = struct.unpack("<i", size_raw)
-        assert size > 0, "%s: We expect to get some non-empty package. Invalid Python mod in Sprint?" % (self,)
-        stream = io.BytesIO()
-        read_size = 0
-        while read_size < size:
-            data_raw = p.read(size - read_size)
-            if len(data_raw) == 0:
-                raise EOFError("%s: expected to read %i bytes but got EOF after %i bytes" % (self, size, read_size))
-            read_size += len(data_raw)
-            stream.write(data_raw)
-        stream.seek(0)
-        return Unpickler(stream).load()
+        return util.read_pickled_object(self.pipe_p2c)
 
     def close(self):
         """
diff --git a/returnn/sprint/error_signals.py b/returnn/sprint/error_signals.py
index ab7d1cb040..bc4de91996 100644
--- a/returnn/sprint/error_signals.py
+++ b/returnn/sprint/error_signals.py
@@ -14,12 +14,11 @@
 import atexit
 import signal
 import typing
-import struct
-import io
 from threading import RLock, Thread
 import returnn.util.task_system as task_system
-from returnn.util.task_system import Pickler, Unpickler, numpy_set_unused
+from returnn.util.task_system import numpy_set_unused
 from returnn.util.basic import eval_shell_str, make_hashable, close_all_fds_except
+import returnn.util.basic as util
 from returnn.log import log
 
 
@@ -219,32 +218,12 @@ def _build_sprint_args(self):
     def _send(self, v):
         assert os.getpid() == self.parent_pid
         p = self.pipe_p2c[1]  # see _start_child
-        stream = io.BytesIO()
-        Pickler(stream).dump(v)
-        raw_data = stream.getvalue()
-        assert len(raw_data) > 0
-        p.write(struct.pack("<i", len(raw_data)))
-        p.write(raw_data)
-        p.flush()
+        util.write_pickled_object(p, v)
 
     def _read(self):
         assert os.getpid() == self.parent_pid
         p = self.pipe_c2p[0]  # see _start_child
-        size_raw = p.read(4)
-        if len(size_raw) < 4:
-            raise EOFError
-        (size,) = struct.unpack("<i", size_raw)
-        assert size > 0, "%s: We expect to get some non-empty package. Invalid Python mod in Sprint?" % (self,)
-        stream = io.BytesIO()
-        read_size = 0
-        while read_size < size:
-            data_raw = p.read(size - read_size)
-            if len(data_raw) == 0:
-                raise EOFError("%s: expected to read %i bytes but got EOF after %i bytes" % (self, size, read_size))
-            read_size += len(data_raw)
-            stream.write(data_raw)
-        stream.seek(0)
-        return Unpickler(stream).load()
+        return util.read_pickled_object(p)
 
     def _poll(self):
         assert os.getpid() == self.parent_pid
diff --git a/returnn/sprint/extern_interface.py b/returnn/sprint/extern_interface.py
index 73395eceef..5b9971c1bd 100644
--- a/returnn/sprint/extern_interface.py
+++ b/returnn/sprint/extern_interface.py
@@ -11,8 +11,8 @@
 import typing
 from returnn.util import better_exchook
 import returnn.util.task_system as task_system
-from returnn.util.task_system import Pickler
-from returnn.util.basic import to_bool, unicode, BytesIO
+from returnn.util.basic import to_bool, unicode
+import returnn.util.basic as util
 
 # Start Sprint PythonSegmentOrder interface. {
 # We use the PythonSegmentOrder just to get an estimate (upper limit) about the number of sequences.
@@ -347,15 +347,7 @@ def _send(self, data_type, args=None):
         :param object args:
         """
         assert data_type is not None
-        import struct
-
-        stream = BytesIO()
-        Pickler(stream).dump((data_type, args))
-        raw_data = stream.getvalue()
-        assert len(raw_data) > 0
-        self.pipe_c2p.write(struct.pack("<i", len(raw_data)))
-        self.pipe_c2p.write(raw_data)
-        self.pipe_c2p.flush()
+        util.write_pickled_object(self.pipe_c2p, (data_type, args))
 
     def add_new_data(self, segment_name, features, targets):
         """
diff --git a/returnn/util/basic.py b/returnn/util/basic.py
index 8ff670a165..ae09178924 100644
--- a/returnn/util/basic.py
+++ b/returnn/util/basic.py
@@ -5,7 +5,7 @@
 """
 
 from __future__ import annotations
-from typing import Optional, Generic, TypeVar, Iterable, Tuple, Dict, List, Callable
+from typing import Optional, Any, Generic, TypeVar, Iterable, Tuple, Dict, List, Callable
 
 import subprocess
 from subprocess import CalledProcessError
@@ -2597,6 +2597,58 @@ def pickle_loads(s):
     return c
 
 
+def read_bytes_to_new_buffer(p: typing.BinaryIO, size: int) -> BytesIO:
+    """
+    Read bytes from stream s into a BytesIO buffer.
+    Raises EOFError if not enough bytes are available.
+    Then read it via :func:`read_pickled_object`.
+    """
+    stream = BytesIO()
+    read_size = 0
+    while read_size < size:
+        data_raw = p.read(size - read_size)
+        if len(data_raw) == 0:
+            raise EOFError("expected to read %i bytes but got EOF after %i bytes" % (size, read_size))
+        read_size += len(data_raw)
+        stream.write(data_raw)
+    stream.seek(0)
+    return stream
+
+
+def read_pickled_object(p: typing.BinaryIO, *, encoding=None) -> Any:
+    """
+    Read pickled object from stream p,
+    after it was written via :func:`read_bytes_to_new_buffer`.
+
+    :param p:
+    :param encoding: if given, passed to Unpickler
+    """
+    from returnn.util.task_system import Unpickler
+    import struct
+
+    size_raw = read_bytes_to_new_buffer(p, 4)
+    (size,) = struct.unpack("<i", size_raw)
+    assert size > 0, "%s: We expect to get some non-empty package. Invalid Python mod in Sprint?" % (self,)
+    stream = read_bytes_to_new_buffer(p, size)
+    unpickler_kwargs = {}
+    if encoding:
+        unpickler_kwargs["encoding"] = encoding
+    return Unpickler(stream, **unpickler_kwargs).load()
+
+
+def write_pickled_object(p: typing.BinaryIO, obj: Any):
+    """
+    Writes pickled object to stream p.
+    """
+    stream = io.BytesIO()
+    Pickler(stream).dump(data)
+    raw_data = stream.getvalue()
+    assert len(raw_data) > 0
+    p.write(struct.pack("<i", len(raw_data)))
+    p.write(raw_data)
+    p.flush()
+
+
 def load_txt_vector(filename):
     """
     Expect line-based text encoding in file.