diff --git a/python/src/input.rs b/python/src/input.rs
index 398e16b..8525fd1 100644
--- a/python/src/input.rs
+++ b/python/src/input.rs
@@ -3,14 +3,16 @@
 use numpy::{
     PyArray1, PyArrayDyn, PyArrayMethods, PyReadonlyArrayDyn, PyUntypedArray, PyUntypedArrayMethods,
 };
+use pyo3::buffer::PyBuffer;
 use pyo3::exceptions::{PyOverflowError, PyTypeError, PyValueError};
 use pyo3::prelude::*;
-use pyo3::types::{PyBool, PyTuple};
+use pyo3::types::{PyBool, PyDict, PyTuple};
 
 use crate::error::{InvalidBitsError, InvalidBlockError, length_mismatch};
 
 const CODES_TYPE: &str = "codes must be a 1-D signed integer array or a sequence of int; packed Quantized.codes is uint8 and must not be passed here — use unpacked_codes";
 const PACKED_CODES_TYPE: &str = "codes must be a 1-D uint8 array, like Quantized.codes";
+const BYTES_TYPE: &str = "data must be bytes, like to_bytes returns, or a 1-D uint8 array";
 const OUT_TYPE: &str = "out must be a writable C-contiguous native-endian float32 array";
 const OUT_CONTIG: &str = "out must be writable and C-contiguous";
 
@@ -39,9 +41,9 @@ pub fn as_f32_values<'py>(obj: &Bound<'py, PyAny>) -> PyResult<PyReadonlyArrayDy
     read_f32(obj, "values", &[1], "a 1-D array").map(|(values, _)| values)
 }
 
-/// Anything that `numpy.asarray` turns into an array works, like a list or a
-/// PyTorch tensor, as long as it holds real numbers and has one of
-/// `dimensions`, which `wanted` describes. Errors call it `argument`. An
+/// Anything that `numpy.asarray` turns into an array works, like a list, and
+/// so does any PyTorch tensor, as long as it holds real numbers and has one
+/// of `dimensions`, which `wanted` describes. Errors call it `argument`. An
 /// array that already holds C-contiguous float32 values is read where it is,
 /// without a copy.
 fn read_f32<'py>(
@@ -56,7 +58,7 @@ fn read_f32<'py>(
             "{argument} can't be a masked array, since its mask would be ignored; fill in the masked values first, like {argument}.filled(0)"
         )));
     }
-    let converted = numpy.call_method1("asarray", (obj,))?;
+    let converted = numpy.call_method1("asarray", (readable_by_numpy(obj)?,))?;
     let array = converted.cast::<PyUntypedArray>()?;
     if !matches!(dtype_kind(array)?.as_str(), "b" | "i" | "u" | "f") {
         return Err(PyTypeError::new_err(format!(
@@ -76,6 +78,34 @@ fn read_f32<'py>(
     Ok((typed.try_readonly()?, array.shape().to_vec()))
 }
 
+/// `obj`, or if it's a PyTorch tensor, a tensor that `numpy.asarray` reads:
+/// detached, since NumPy refuses one that requires grad, and in float32 if
+/// it holds floating-point numbers, since NumPy has no bfloat16.
+fn readable_by_numpy<'py>(obj: &Bound<'py, PyAny>) -> PyResult<Bound<'py, PyAny>> {
+    if !is_torch_tensor(obj)? {
+        return Ok(obj.clone());
+    }
+    let tensor = obj.call_method0("detach")?;
+    if tensor.call_method0("is_floating_point")?.is_truthy()? {
+        return tensor.call_method0("float");
+    }
+    Ok(tensor)
+}
+
+/// Whether `obj` is a PyTorch tensor. A program that passes one has imported
+/// torch, so torch is looked up in `sys.modules` instead of imported, and
+/// NumPy arrays, the usual input, skip even that.
+fn is_torch_tensor(obj: &Bound<'_, PyAny>) -> PyResult<bool> {
+    if obj.is_instance_of::<PyUntypedArray>() {
+        return Ok(false);
+    }
+    let modules = obj.py().import("sys")?.getattr("modules")?;
+    match modules.cast::<PyDict>()?.get_item("torch")? {
+        Some(torch) if !torch.is_none() => obj.is_instance(&torch.getattr("Tensor")?),
+        _ => Ok(false),
+    }
+}
+
 /// `obj`'s type, and the shape and dtype that `numpy.asarray` gave it, such
 /// as `torch.Tensor with shape (2, 3, 4) and dtype float32`.
 fn describe(obj: &Bound<'_, PyAny>, array: &Bound<'_, PyUntypedArray>) -> PyResult<String> {
@@ -153,10 +183,26 @@ pub fn as_i32_codes(obj: &Bound<'_, PyAny>) -> PyResult<Vec<i32>> {
 
 /// Read packed codes: a 1-D uint8 array, like `Quantized.codes` returns.
 pub fn as_packed_codes(obj: &Bound<'_, PyAny>) -> PyResult<Vec<u8>> {
-    let codes = obj
+    read_uint8(obj, PACKED_CODES_TYPE)
+}
+
+/// Read the bytes that `to_bytes` saved: `bytes` or another bytes-like
+/// object, or a 1-D uint8 array.
+pub fn as_bytes(obj: &Bound<'_, PyAny>) -> PyResult<Vec<u8>> {
+    match PyBuffer::<u8>::get(obj) {
+        Ok(buffer) => buffer.to_vec(obj.py()),
+        Err(_) => read_uint8(obj, BYTES_TYPE),
+    }
+}
+
+/// Read a 1-D uint8 array, or anything that `numpy.asarray` turns into one,
+/// like a PyTorch tensor. Anything else raises `TypeError(message)`.
+fn read_uint8(obj: &Bound<'_, PyAny>, message: &'static str) -> PyResult<Vec<u8>> {
+    let array = obj.py().import("numpy")?.call_method1("asarray", (obj,))?;
+    let bytes = array
         .cast::<PyArray1<u8>>()
-        .map_err(|_| PyTypeError::new_err(PACKED_CODES_TYPE))?;
-    Ok(codes.try_readonly()?.as_array().to_vec())
+        .map_err(|_| PyTypeError::new_err(message))?;
+    Ok(bytes.try_readonly()?.as_array().to_vec())
 }
 
 /// Borrow `out` for writing, after checking it has exactly `shape`.
diff --git a/python/src/quantized/methods.rs b/python/src/quantized/methods.rs
index 57a4f2f..cefc26b 100644
--- a/python/src/quantized/methods.rs
+++ b/python/src/quantized/methods.rs
@@ -1,5 +1,4 @@
 use numpy::{IntoPyArray, PyArray1, PyArrayMethods};
-use pyo3::buffer::PyBuffer;
 use pyo3::exceptions::PyValueError;
 use pyo3::prelude::*;
 use pyo3::types::{PyBytes, PyTuple, PyType};
@@ -10,8 +9,8 @@ use super::inner::{PyQuantized, QuantizedInner, with_inner};
 use super::parts::Parts;
 use crate::error::from_quantize;
 use crate::input::{
-    as_f32_array, as_f32_matmul_values, as_f32_values, as_packed_codes, as_writable_f32_out,
-    check_shape,
+    as_bytes, as_f32_array, as_f32_matmul_values, as_f32_values, as_packed_codes,
+    as_writable_f32_out, check_shape,
 };
 use crate::scale::PyScale;
 
@@ -275,17 +274,18 @@ impl PyQuantized {
     }
 
     /// Load a tensor that `to_bytes` saved, in Python or in Rust. `data` is
-    /// `bytes` or another bytes-like object, such as a uint8 NumPy array.
-    /// Bytes that don't hold a valid tensor raise `QuantizeError`.
+    /// `bytes` or another bytes-like object, or a 1-D uint8 array, such as a
+    /// NumPy array or the PyTorch tensor that safetensors loads. Bytes that
+    /// don't hold a valid tensor raise `QuantizeError`.
     #[staticmethod]
-    fn from_bytes(py: Python<'_>, data: PyBuffer<u8>) -> PyResult<Self> {
-        let inner = QuantizedInner::from_bytes(&data.to_vec(py)?).map_err(from_quantize)?;
+    fn from_bytes(data: Bound<'_, PyAny>) -> PyResult<Self> {
+        let inner = QuantizedInner::from_bytes(&as_bytes(&data)?).map_err(from_quantize)?;
         Ok(Self { inner })
     }
 
     #[new]
-    fn new(py: Python<'_>, data: PyBuffer<u8>) -> PyResult<Self> {
-        Self::from_bytes(py, data)
+    fn new(data: Bound<'_, PyAny>) -> PyResult<Self> {
+        Self::from_bytes(data)
     }
 
     fn __repr__(&self, py: Python<'_>) -> PyResult<String> {
diff --git a/python/tests/test_quantize.py b/python/tests/test_quantize.py
index 27fdcb9..d7a61d2 100644
--- a/python/tests/test_quantize.py
+++ b/python/tests/test_quantize.py
@@ -3,6 +3,8 @@
 import io
 import pickle
 import re
+import sys
+import types
 from collections.abc import Hashable
 
 import numpy as np
@@ -179,6 +181,63 @@ def test_quantize_reads_anything_numpy_asarray_reads():
     assert quantize(Tensor(weights)).matmul(Tensor(weights[:2])).shape == (2, 4)
 
 
+class TorchTensor(Tensor):
+    """Stands in for a PyTorch tensor, which NumPy can't read while it
+    requires grad or holds bfloat16."""
+
+    def __init__(self, values, requires_grad=False, dtype="float32"):
+        super().__init__(values)
+        self.requires_grad = requires_grad
+        self.dtype = dtype
+
+    def __array__(self, dtype=None, copy=None):
+        if self.requires_grad:
+            raise RuntimeError("Can't call numpy() on Tensor that requires grad.")
+        if self.dtype == "bfloat16":
+            raise TypeError("Got unsupported ScalarType BFloat16")
+        return self.values
+
+    def detach(self):
+        return TorchTensor(self.values, dtype=self.dtype)
+
+    def is_floating_point(self):
+        return self.values.dtype.kind == "f"
+
+    def float(self):
+        return TorchTensor(self.values, self.requires_grad)
+
+
+def test_torch_tensors_are_read_even_if_they_require_grad_or_hold_bfloat16(monkeypatch):
+    monkeypatch.setitem(sys.modules, "torch", types.SimpleNamespace(Tensor=TorchTensor))
+    weights = weight_matrix(4, 32)
+    expected = quantize(weights)
+    for tensor in [TorchTensor(weights, requires_grad=True), TorchTensor(weights, dtype="bfloat16")]:
+        assert quantize(tensor) == expected
+        assert expected.dot(tensor) == expected.dot(weights)
+    # Some programs keep torch from being imported this way.
+    monkeypatch.setitem(sys.modules, "torch", None)
+    assert quantize(weights.tolist()) == expected
+
+
+def test_bytes_and_codes_can_be_any_uint8_array_that_numpy_asarray_reads():
+    quantized = quantize(weight_matrix(4, 32), bits=4)
+    data = Tensor(np.frombuffer(quantized.to_bytes(), np.uint8))
+    assert Quantized.from_bytes(data) == Quantized(data) == quantized
+    rebuilt = Quantized.from_parts(
+        kind="symmetric",
+        shape=(4, 32),
+        block=32,
+        bits=4,
+        codes=Tensor(quantized.codes),
+        scales=quantized.scales,
+        scale="f32",
+    )
+    assert rebuilt == quantized
+    for wrong in [Tensor(quantized.unpacked_codes), "QNTZ", [81, 78, 84, 90]]:
+        with pytest.raises(TypeError, match="data must be bytes, like to_bytes returns, or a 1-D uint8"):
+            Quantized.from_bytes(wrong)
+
+
 def test_values_that_are_not_real_numbers_are_rejected_with_what_arrived():
     for values, dtype in [(np.array([1 + 2j]), "complex128"), (b"ab", "|S2"), ("0.5", "<U3")]:
         with pytest.raises(TypeError, match=f"real numbers, got .* dtype {re.escape(dtype)}"):