diff --git a/tools/python/BUILD b/tools/python/BUILD
index 9939653..37101f5 100644
--- a/tools/python/BUILD
+++ b/tools/python/BUILD
@@ -1,4 +1,5 @@
 load("@rules_python//python:defs.bzl", "py_runtime_pair")
+load("@rules_python//python:pip.bzl", "compile_pip_requirements")
 
 py_runtime(
     name = "python3_runtime",
@@ -25,7 +26,52 @@
     target_compatible_with = [
         "@platforms//cpu:x86_64",
         "@platforms//os:linux",
+        "//tools/platforms/python:debian_bundled_python",
     ],
     toolchain = ":py_runtime",
     toolchain_type = "@rules_python//python:toolchain_type",
 )
+
+# Invoke this via "bazel run //tools/python:requirements.update".
+compile_pip_requirements(
+    name = "requirements",
+    requirements_in = "requirements.txt",
+    requirements_txt = "requirements.lock.txt",
+    tags = [
+        # The test pings pypi.org to make sure that the lock file matches the
+        # requirements file.
+        # TODO(phil): Disable this if it's too flaky.
+        "requires-network",
+    ],
+)
+
+py_runtime(
+    name = "upstream_python3_runtime",
+    files = [
+        "runtime_binary.sh",
+        "@python3_9_x86_64-unknown-linux-gnu//:files",
+    ],
+    interpreter = "runtime_binary.sh",
+    python_version = "PY3",
+)
+
+py_runtime_pair(
+    name = "upstream_py_runtime",
+    py2_runtime = None,
+    py3_runtime = ":upstream_python3_runtime",
+)
+
+toolchain(
+    name = "upstream_python_toolchain",
+    exec_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+    ],
+    target_compatible_with = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:linux",
+        "//tools/platforms/python:upstream_bundled_python",
+    ],
+    toolchain = ":upstream_py_runtime",
+    toolchain_type = "@rules_python//python:toolchain_type",
+)
diff --git a/tools/python/pip_configure.py b/tools/python/pip_configure.py
new file mode 100644
index 0000000..4f9dff1
--- /dev/null
+++ b/tools/python/pip_configure.py
@@ -0,0 +1,80 @@
+"""This script generates contents of the @pip repository.
+
+This repository is just a way to have simple-to-write targets to specify in
+BUILD files.  E.g. you can use @pip//numpy.
+
+The pip package names are normalized:
+- Letters are lowercased.
+- Periods are replaced by underscores.
+- Dashes are replaced by underscores.
+
+We do this normalization because it produces predictable names. pip allows a
+wide range of names to refer to the same package. That would be annoying to use
+in BUILD files.
+"""
+
+import sys
+import textwrap
+from pathlib import Path
+
+
+def parse_requirements(requirements_path: Path) -> list[str]:
+    """Parses tools/python/requirements.txt.
+
+    We don't want to parse the lock file since we really only want users to
+    depend on explicitly requested pip packages. We don't want users to depend
+    on transitive dependencies of our requested pip packages.
+    """
+    result = []
+    for line in requirements_path.read_text().splitlines():
+        # Ignore line comments.
+        if not line or line.startswith("#"):
+            continue
+
+        # Remove any inline comments that may or may not exist.
+        # E.g:
+        # numpy==1.2.3  # needed because we like it.
+        result.append(line.split()[0])
+
+    return result
+
+
+def generate_build_files(requirements: list[str]) -> None:
+    """Generate all the BUILD files in the "pip" external repository.
+
+    We create files like this:
+
+        external/pip/numpy/BUILD
+
+    and in that BUILD file we create a "numpy" target. That lets users depend
+    on "@pip//numpy".
+    """
+    for requirement in requirements:
+        requirement = requirement.lower().replace("-", "_").replace(".", "_")
+        requirement_dir = Path(requirement)
+        requirement_dir.mkdir()
+        # We could use an alias() here, but that behaves strangely with
+        # target_compatible_with pre-6.0.
+        (requirement_dir / "BUILD").write_text(
+            textwrap.dedent(f"""\
+            load("@pip_deps//:requirements.bzl", "requirement")
+            py_library(
+                name = "{requirement}",
+                deps = [requirement("{requirement}")],
+                visibility = ["//visibility:public"],
+                target_compatible_with = [
+                    "@//tools/platforms/python:upstream_bundled_python",
+                ],
+            )
+            """))
+
+
+def main(argv):
+    requirements_path = Path(argv[1])
+    requirements = parse_requirements(requirements_path)
+
+    generate_build_files(requirements)
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))
diff --git a/tools/python/repo_defs.bzl b/tools/python/repo_defs.bzl
new file mode 100644
index 0000000..c0c212b
--- /dev/null
+++ b/tools/python/repo_defs.bzl
@@ -0,0 +1,33 @@
+def _pip_configure_impl(repository_ctx):
+    """Runs tools/python/pip_configure.py."""
+    script_path = repository_ctx.path(repository_ctx.attr._script).realpath
+    interpreter_path = repository_ctx.path(repository_ctx.attr._interpreter).realpath
+    requirements_path = repository_ctx.path(repository_ctx.attr._requirements).realpath
+
+    script_result = repository_ctx.execute([
+        interpreter_path,
+        "-BSs",
+        script_path,
+        requirements_path,
+    ])
+    if script_result.return_code != 0:
+        fail("{} failed: {} ({})".format(
+            script_path,
+            script_result.stdout,
+            script_result.stderr,
+        ))
+
+pip_configure = repository_rule(
+    implementation = _pip_configure_impl,
+    attrs = {
+        "_interpreter": attr.label(
+            default = "@python3_9_x86_64-unknown-linux-gnu//:bin/python3",
+        ),
+        "_script": attr.label(
+            default = "@//tools/python:pip_configure.py",
+        ),
+        "_requirements": attr.label(
+            default = "@//tools/python:requirements.txt",
+        ),
+    },
+)
diff --git a/tools/python/requirements.lock.txt b/tools/python/requirements.lock.txt
new file mode 100644
index 0000000..337eaf8
--- /dev/null
+++ b/tools/python/requirements.lock.txt
@@ -0,0 +1,224 @@
+#
+# This file is autogenerated by pip-compile with python 3.9
+# To update, run:
+#
+#    bazel run //tools/python:requirements.update
+#
+cycler==0.11.0 \
+    --hash=sha256:3a27e95f763a428a739d2add979fa7494c912a32c17c4c38c4d5f082cad165a3 \
+    --hash=sha256:9c87405839a19696e837b3b818fed3f5f69f16f1eec1a1ad77e043dcea9c772f
+    # via matplotlib
+fonttools==4.28.5 \
+    --hash=sha256:545c05d0f7903a863c2020e07b8f0a57517f2c40d940bded77076397872d14ca \
+    --hash=sha256:edf251d5d2cc0580d5f72de4621c338d8c66c5f61abb50cf486640f73c8194d5
+    # via matplotlib
+kiwisolver==1.3.2 \
+    --hash=sha256:0007840186bacfaa0aba4466d5890334ea5938e0bb7e28078a0eb0e63b5b59d5 \
+    --hash=sha256:19554bd8d54cf41139f376753af1a644b63c9ca93f8f72009d50a2080f870f77 \
+    --hash=sha256:1d45d1c74f88b9f41062716c727f78f2a59a5476ecbe74956fafb423c5c87a76 \
+    --hash=sha256:1d819553730d3c2724582124aee8a03c846ec4362ded1034c16fb3ef309264e6 \
+    --hash=sha256:2210f28778c7d2ee13f3c2a20a3a22db889e75f4ec13a21072eabb5693801e84 \
+    --hash=sha256:22521219ca739654a296eea6d4367703558fba16f98688bd8ce65abff36eaa84 \
+    --hash=sha256:25405f88a37c5f5bcba01c6e350086d65e7465fd1caaf986333d2a045045a223 \
+    --hash=sha256:2b65bd35f3e06a47b5c30ea99e0c2b88f72c6476eedaf8cfbc8e66adb5479dcf \
+    --hash=sha256:2ddb500a2808c100e72c075cbb00bf32e62763c82b6a882d403f01a119e3f402 \
+    --hash=sha256:2f8f6c8f4f1cff93ca5058d6ec5f0efda922ecb3f4c5fb76181f327decff98b8 \
+    --hash=sha256:30fa008c172355c7768159983a7270cb23838c4d7db73d6c0f6b60dde0d432c6 \
+    --hash=sha256:3dbb3cea20b4af4f49f84cffaf45dd5f88e8594d18568e0225e6ad9dec0e7967 \
+    --hash=sha256:4116ba9a58109ed5e4cb315bdcbff9838f3159d099ba5259c7c7fb77f8537492 \
+    --hash=sha256:44e6adf67577dbdfa2d9f06db9fbc5639afefdb5bf2b4dfec25c3a7fbc619536 \
+    --hash=sha256:5326ddfacbe51abf9469fe668944bc2e399181a2158cb5d45e1d40856b2a0589 \
+    --hash=sha256:70adc3658138bc77a36ce769f5f183169bc0a2906a4f61f09673f7181255ac9b \
+    --hash=sha256:72be6ebb4e92520b9726d7146bc9c9b277513a57a38efcf66db0620aec0097e0 \
+    --hash=sha256:7843b1624d6ccca403a610d1277f7c28ad184c5aa88a1750c1a999754e65b439 \
+    --hash=sha256:7ba5a1041480c6e0a8b11a9544d53562abc2d19220bfa14133e0cdd9967e97af \
+    --hash=sha256:80efd202108c3a4150e042b269f7c78643420cc232a0a771743bb96b742f838f \
+    --hash=sha256:82f49c5a79d3839bc8f38cb5f4bfc87e15f04cbafa5fbd12fb32c941cb529cfb \
+    --hash=sha256:83d2c9db5dfc537d0171e32de160461230eb14663299b7e6d18ca6dca21e4977 \
+    --hash=sha256:8d93a1095f83e908fc253f2fb569c2711414c0bfd451cab580466465b235b470 \
+    --hash=sha256:8dc3d842fa41a33fe83d9f5c66c0cc1f28756530cd89944b63b072281e852031 \
+    --hash=sha256:9661a04ca3c950a8ac8c47f53cbc0b530bce1b52f516a1e87b7736fec24bfff0 \
+    --hash=sha256:a498bcd005e8a3fedd0022bb30ee0ad92728154a8798b703f394484452550507 \
+    --hash=sha256:a7a4cf5bbdc861987a7745aed7a536c6405256853c94abc9f3287c3fa401b174 \
+    --hash=sha256:b5074fb09429f2b7bc82b6fb4be8645dcbac14e592128beeff5461dcde0af09f \
+    --hash=sha256:b6a5431940f28b6de123de42f0eb47b84a073ee3c3345dc109ad550a3307dd28 \
+    --hash=sha256:ba677bcaff9429fd1bf01648ad0901cea56c0d068df383d5f5856d88221fe75b \
+    --hash=sha256:bcadb05c3d4794eb9eee1dddf1c24215c92fb7b55a80beae7a60530a91060560 \
+    --hash=sha256:bf7eb45d14fc036514c09554bf983f2a72323254912ed0c3c8e697b62c4c158f \
+    --hash=sha256:c358721aebd40c243894298f685a19eb0491a5c3e0b923b9f887ef1193ddf829 \
+    --hash=sha256:c4550a359c5157aaf8507e6820d98682872b9100ce7607f8aa070b4b8af6c298 \
+    --hash=sha256:c6572c2dab23c86a14e82c245473d45b4c515314f1f859e92608dcafbd2f19b8 \
+    --hash=sha256:cba430db673c29376135e695c6e2501c44c256a81495da849e85d1793ee975ad \
+    --hash=sha256:dedc71c8eb9c5096037766390172c34fb86ef048b8e8958b4e484b9e505d66bc \
+    --hash=sha256:e6f5eb2f53fac7d408a45fbcdeda7224b1cfff64919d0f95473420a931347ae9 \
+    --hash=sha256:ec2eba188c1906b05b9b49ae55aae4efd8150c61ba450e6721f64620c50b59eb \
+    --hash=sha256:ee040a7de8d295dbd261ef2d6d3192f13e2b08ec4a954de34a6fb8ff6422e24c \
+    --hash=sha256:eedd3b59190885d1ebdf6c5e0ca56828beb1949b4dfe6e5d0256a461429ac386 \
+    --hash=sha256:f441422bb313ab25de7b3dbfd388e790eceb76ce01a18199ec4944b369017009 \
+    --hash=sha256:f8eb7b6716f5b50e9c06207a14172cf2de201e41912ebe732846c02c830455b9 \
+    --hash=sha256:fc4453705b81d03568d5b808ad8f09c77c47534f6ac2e72e733f9ca4714aa75c
+    # via matplotlib
+matplotlib==3.5.1 \
+    --hash=sha256:14334b9902ec776461c4b8c6516e26b450f7ebe0b3ef8703bf5cdfbbaecf774a \
+    --hash=sha256:2252bfac85cec7af4a67e494bfccf9080bcba8a0299701eab075f48847cca907 \
+    --hash=sha256:2e3484d8455af3fdb0424eae1789af61f6a79da0c80079125112fd5c1b604218 \
+    --hash=sha256:34a1fc29f8f96e78ec57a5eff5e8d8b53d3298c3be6df61e7aa9efba26929522 \
+    --hash=sha256:3e66497cd990b1a130e21919b004da2f1dc112132c01ac78011a90a0f9229778 \
+    --hash=sha256:40e0d7df05e8efe60397c69b467fc8f87a2affeb4d562fe92b72ff8937a2b511 \
+    --hash=sha256:456cc8334f6d1124e8ff856b42d2cc1c84335375a16448189999496549f7182b \
+    --hash=sha256:506b210cc6e66a0d1c2bb765d055f4f6bc2745070fb1129203b67e85bbfa5c18 \
+    --hash=sha256:53273c5487d1c19c3bc03b9eb82adaf8456f243b97ed79d09dded747abaf1235 \
+    --hash=sha256:577ed20ec9a18d6bdedb4616f5e9e957b4c08563a9f985563a31fd5b10564d2a \
+    --hash=sha256:6803299cbf4665eca14428d9e886de62e24f4223ac31ab9c5d6d5339a39782c7 \
+    --hash=sha256:68fa30cec89b6139dc559ed6ef226c53fd80396da1919a1b5ef672c911aaa767 \
+    --hash=sha256:6c094e4bfecd2fa7f9adffd03d8abceed7157c928c2976899de282f3600f0a3d \
+    --hash=sha256:778d398c4866d8e36ee3bf833779c940b5f57192fa0a549b3ad67bc4c822771b \
+    --hash=sha256:7a350ca685d9f594123f652ba796ee37219bf72c8e0fc4b471473d87121d6d34 \
+    --hash=sha256:87900c67c0f1728e6db17c6809ec05c025c6624dcf96a8020326ea15378fe8e7 \
+    --hash=sha256:8a77906dc2ef9b67407cec0bdbf08e3971141e535db888974a915be5e1e3efc6 \
+    --hash=sha256:8e70ae6475cfd0fad3816dcbf6cac536dc6f100f7474be58d59fa306e6e768a4 \
+    --hash=sha256:abf67e05a1b7f86583f6ebd01f69b693b9c535276f4e943292e444855870a1b8 \
+    --hash=sha256:b04fc29bcef04d4e2d626af28d9d892be6aba94856cb46ed52bcb219ceac8943 \
+    --hash=sha256:b19a761b948e939a9e20173aaae76070025f0024fc8f7ba08bef22a5c8573afc \
+    --hash=sha256:b2e9810e09c3a47b73ce9cab5a72243a1258f61e7900969097a817232246ce1c \
+    --hash=sha256:b71f3a7ca935fc759f2aed7cec06cfe10bc3100fadb5dbd9c435b04e557971e1 \
+    --hash=sha256:b8a4fb2a0c5afbe9604f8a91d7d0f27b1832c3e0b5e365f95a13015822b4cd65 \
+    --hash=sha256:bb1c613908f11bac270bc7494d68b1ef6e7c224b7a4204d5dacf3522a41e2bc3 \
+    --hash=sha256:d24e5bb8028541ce25e59390122f5e48c8506b7e35587e5135efcb6471b4ac6c \
+    --hash=sha256:d70a32ee1f8b55eed3fd4e892f0286df8cccc7e0475c11d33b5d0a148f5c7599 \
+    --hash=sha256:e293b16cf303fe82995e41700d172a58a15efc5331125d08246b520843ef21ee \
+    --hash=sha256:e2f28a07b4f82abb40267864ad7b3a4ed76f1b1663e81c7efc84a9b9248f672f \
+    --hash=sha256:e3520a274a0e054e919f5b3279ee5dbccf5311833819ccf3399dab7c83e90a25 \
+    --hash=sha256:e3b6f3fd0d8ca37861c31e9a7cab71a0ef14c639b4c95654ea1dd153158bf0df \
+    --hash=sha256:e486f60db0cd1c8d68464d9484fd2a94011c1ac8593d765d0211f9daba2bd535 \
+    --hash=sha256:e8c87cdaf06fd7b2477f68909838ff4176f105064a72ca9d24d3f2a29f73d393 \
+    --hash=sha256:edf5e4e1d5fb22c18820e8586fb867455de3b109c309cb4fce3aaed85d9468d1 \
+    --hash=sha256:fe8d40c434a8e2c68d64c6d6a04e77f21791a93ff6afe0dce169597c110d3079
+    # via -r tools/python/requirements.txt
+numpy==1.21.5 \
+    --hash=sha256:00c9fa73a6989895b8815d98300a20ac993c49ac36c8277e8ffeaa3631c0dbbb \
+    --hash=sha256:025b497014bc33fc23897859350f284323f32a2fff7654697f5a5fc2a19e9939 \
+    --hash=sha256:08de8472d9f7571f9d51b27b75e827f5296295fa78817032e84464be8bb905bc \
+    --hash=sha256:1964db2d4a00348b7a60ee9d013c8cb0c566644a589eaa80995126eac3b99ced \
+    --hash=sha256:2a9add27d7fc0fdb572abc3b2486eb3b1395da71e0254c5552b2aad2a18b5441 \
+    --hash=sha256:2d8adfca843bc46ac199a4645233f13abf2011a0b2f4affc5c37cd552626f27b \
+    --hash=sha256:301e408a052fdcda5cdcf03021ebafc3c6ea093021bf9d1aa47c54d48bdad166 \
+    --hash=sha256:311283acf880cfcc20369201bd75da907909afc4666966c7895cbed6f9d2c640 \
+    --hash=sha256:341dddcfe3b7b6427a28a27baa59af5ad51baa59bfec3264f1ab287aa3b30b13 \
+    --hash=sha256:3a5098df115340fb17fc93867317a947e1dcd978c3888c5ddb118366095851f8 \
+    --hash=sha256:3c978544be9e04ed12016dd295a74283773149b48f507d69b36f91aa90a643e5 \
+    --hash=sha256:3d893b0871322eaa2f8c7072cdb552d8e2b27645b7875a70833c31e9274d4611 \
+    --hash=sha256:4fe6a006557b87b352c04596a6e3f12a57d6e5f401d804947bd3188e6b0e0e76 \
+    --hash=sha256:507c05c7a37b3683eb08a3ff993bd1ee1e6c752f77c2f275260533b265ecdb6c \
+    --hash=sha256:58ca1d7c8aef6e996112d0ce873ac9dfa1eaf4a1196b4ff7ff73880a09923ba7 \
+    --hash=sha256:61bada43d494515d5b122f4532af226fdb5ee08fe5b5918b111279843dc6836a \
+    --hash=sha256:69a5a8d71c308d7ef33ef72371c2388a90e3495dbb7993430e674006f94797d5 \
+    --hash=sha256:6a5928bc6241264dce5ed509e66f33676fc97f464e7a919edc672fb5532221ee \
+    --hash=sha256:7b9d6b14fc9a4864b08d1ba57d732b248f0e482c7b2ff55c313137e3ed4d8449 \
+    --hash=sha256:a7c4b701ca418cd39e28ec3b496e6388fe06de83f5f0cb74794fa31cfa384c02 \
+    --hash=sha256:a7e8f6216f180f3fd4efb73de5d1eaefb5f5a1ee5b645c67333033e39440e63a \
+    --hash=sha256:b545ebadaa2b878c8630e5bcdb97fc4096e779f335fc0f943547c1c91540c815 \
+    --hash=sha256:c293d3c0321996cd8ffe84215ffe5d269fd9d1d12c6f4ffe2b597a7c30d3e593 \
+    --hash=sha256:c5562bcc1a9b61960fc8950ade44d00e3de28f891af0acc96307c73613d18f6e \
+    --hash=sha256:ca9c23848292c6fe0a19d212790e62f398fd9609aaa838859be8459bfbe558aa \
+    --hash=sha256:cc1b30205d138d1005adb52087ff45708febbef0e420386f58664f984ef56954 \
+    --hash=sha256:dbce7adeb66b895c6aaa1fad796aaefc299ced597f6fbd9ceddb0dd735245354 \
+    --hash=sha256:dc4b2fb01f1b4ddbe2453468ea0719f4dbb1f5caa712c8b21bb3dd1480cd30d9 \
+    --hash=sha256:eed2afaa97ec33b4411995be12f8bdb95c87984eaa28d76cf628970c8a2d689a \
+    --hash=sha256:fc7a7d7b0ed72589fd8b8486b9b42a564f10b8762be8bd4d9df94b807af4a089
+    # via
+    #   -r tools/python/requirements.txt
+    #   matplotlib
+    #   scipy
+packaging==21.3 \
+    --hash=sha256:dd47c42927d89ab911e606518907cc2d3a1f38bbd026385970643f9c5b8ecfeb \
+    --hash=sha256:ef103e05f519cdc783ae24ea4e2e0f508a9c99b2d4969652eed6a2e1ea5bd522
+    # via matplotlib
+pillow==8.4.0 \
+    --hash=sha256:066f3999cb3b070a95c3652712cffa1a748cd02d60ad7b4e485c3748a04d9d76 \
+    --hash=sha256:0a0956fdc5defc34462bb1c765ee88d933239f9a94bc37d132004775241a7585 \
+    --hash=sha256:0b052a619a8bfcf26bd8b3f48f45283f9e977890263e4571f2393ed8898d331b \
+    --hash=sha256:1394a6ad5abc838c5cd8a92c5a07535648cdf6d09e8e2d6df916dfa9ea86ead8 \
+    --hash=sha256:1bc723b434fbc4ab50bb68e11e93ce5fb69866ad621e3c2c9bdb0cd70e345f55 \
+    --hash=sha256:244cf3b97802c34c41905d22810846802a3329ddcb93ccc432870243211c79fc \
+    --hash=sha256:25a49dc2e2f74e65efaa32b153527fc5ac98508d502fa46e74fa4fd678ed6645 \
+    --hash=sha256:2e4440b8f00f504ee4b53fe30f4e381aae30b0568193be305256b1462216feff \
+    --hash=sha256:3862b7256046fcd950618ed22d1d60b842e3a40a48236a5498746f21189afbbc \
+    --hash=sha256:3eb1ce5f65908556c2d8685a8f0a6e989d887ec4057326f6c22b24e8a172c66b \
+    --hash=sha256:3f97cfb1e5a392d75dd8b9fd274d205404729923840ca94ca45a0af57e13dbe6 \
+    --hash=sha256:493cb4e415f44cd601fcec11c99836f707bb714ab03f5ed46ac25713baf0ff20 \
+    --hash=sha256:4acc0985ddf39d1bc969a9220b51d94ed51695d455c228d8ac29fcdb25810e6e \
+    --hash=sha256:5503c86916d27c2e101b7f71c2ae2cddba01a2cf55b8395b0255fd33fa4d1f1a \
+    --hash=sha256:5b7bb9de00197fb4261825c15551adf7605cf14a80badf1761d61e59da347779 \
+    --hash=sha256:5e9ac5f66616b87d4da618a20ab0a38324dbe88d8a39b55be8964eb520021e02 \
+    --hash=sha256:620582db2a85b2df5f8a82ddeb52116560d7e5e6b055095f04ad828d1b0baa39 \
+    --hash=sha256:62cc1afda735a8d109007164714e73771b499768b9bb5afcbbee9d0ff374b43f \
+    --hash=sha256:70ad9e5c6cb9b8487280a02c0ad8a51581dcbbe8484ce058477692a27c151c0a \
+    --hash=sha256:72b9e656e340447f827885b8d7a15fc8c4e68d410dc2297ef6787eec0f0ea409 \
+    --hash=sha256:72cbcfd54df6caf85cc35264c77ede902452d6df41166010262374155947460c \
+    --hash=sha256:792e5c12376594bfcb986ebf3855aa4b7c225754e9a9521298e460e92fb4a488 \
+    --hash=sha256:7b7017b61bbcdd7f6363aeceb881e23c46583739cb69a3ab39cb384f6ec82e5b \
+    --hash=sha256:81f8d5c81e483a9442d72d182e1fb6dcb9723f289a57e8030811bac9ea3fef8d \
+    --hash=sha256:82aafa8d5eb68c8463b6e9baeb4f19043bb31fefc03eb7b216b51e6a9981ae09 \
+    --hash=sha256:84c471a734240653a0ec91dec0996696eea227eafe72a33bd06c92697728046b \
+    --hash=sha256:8c803ac3c28bbc53763e6825746f05cc407b20e4a69d0122e526a582e3b5e153 \
+    --hash=sha256:93ce9e955cc95959df98505e4608ad98281fff037350d8c2671c9aa86bcf10a9 \
+    --hash=sha256:9a3e5ddc44c14042f0844b8cf7d2cd455f6cc80fd7f5eefbe657292cf601d9ad \
+    --hash=sha256:a4901622493f88b1a29bd30ec1a2f683782e57c3c16a2dbc7f2595ba01f639df \
+    --hash=sha256:a5a4532a12314149d8b4e4ad8ff09dde7427731fcfa5917ff16d0291f13609df \
+    --hash=sha256:b8831cb7332eda5dc89b21a7bce7ef6ad305548820595033a4b03cf3091235ed \
+    --hash=sha256:b8e2f83c56e141920c39464b852de3719dfbfb6e3c99a2d8da0edf4fb33176ed \
+    --hash=sha256:c70e94281588ef053ae8998039610dbd71bc509e4acbc77ab59d7d2937b10698 \
+    --hash=sha256:c8a17b5d948f4ceeceb66384727dde11b240736fddeda54ca740b9b8b1556b29 \
+    --hash=sha256:d82cdb63100ef5eedb8391732375e6d05993b765f72cb34311fab92103314649 \
+    --hash=sha256:d89363f02658e253dbd171f7c3716a5d340a24ee82d38aab9183f7fdf0cdca49 \
+    --hash=sha256:d99ec152570e4196772e7a8e4ba5320d2d27bf22fdf11743dd882936ed64305b \
+    --hash=sha256:ddc4d832a0f0b4c52fff973a0d44b6c99839a9d016fe4e6a1cb8f3eea96479c2 \
+    --hash=sha256:e3dacecfbeec9a33e932f00c6cd7996e62f53ad46fbe677577394aaa90ee419a \
+    --hash=sha256:eb9fc393f3c61f9054e1ed26e6fe912c7321af2f41ff49d3f83d05bacf22cc78
+    # via matplotlib
+pyparsing==3.0.6 \
+    --hash=sha256:04ff808a5b90911829c55c4e26f75fa5ca8a2f5f36aa3a51f68e27033341d3e4 \
+    --hash=sha256:d9bdec0013ef1eb5a84ab39a3b3868911598afa494f5faa038647101504e2b81
+    # via
+    #   matplotlib
+    #   packaging
+python-dateutil==2.8.2 \
+    --hash=sha256:0123cacc1627ae19ddf3c27a5de5bd67ee4586fbdd6440d9748f8abb483d3e86 \
+    --hash=sha256:961d03dc3453ebbc59dbdea9e4e11c5651520a876d0f4db161e8674aae935da9
+    # via matplotlib
+scipy==1.7.3 \
+    --hash=sha256:033ce76ed4e9f62923e1f8124f7e2b0800db533828c853b402c7eec6e9465d80 \
+    --hash=sha256:173308efba2270dcd61cd45a30dfded6ec0085b4b6eb33b5eb11ab443005e088 \
+    --hash=sha256:21b66200cf44b1c3e86495e3a436fc7a26608f92b8d43d344457c54f1c024cbc \
+    --hash=sha256:2c56b820d304dffcadbbb6cbfbc2e2c79ee46ea291db17e288e73cd3c64fefa9 \
+    --hash=sha256:304dfaa7146cffdb75fbf6bb7c190fd7688795389ad060b970269c8576d038e9 \
+    --hash=sha256:3f78181a153fa21c018d346f595edd648344751d7f03ab94b398be2ad083ed3e \
+    --hash=sha256:4d242d13206ca4302d83d8a6388c9dfce49fc48fdd3c20efad89ba12f785bf9e \
+    --hash=sha256:5d1cc2c19afe3b5a546ede7e6a44ce1ff52e443d12b231823268019f608b9b12 \
+    --hash=sha256:5f2cfc359379c56b3a41b17ebd024109b2049f878badc1e454f31418c3a18436 \
+    --hash=sha256:65bd52bf55f9a1071398557394203d881384d27b9c2cad7df9a027170aeaef93 \
+    --hash=sha256:7edd9a311299a61e9919ea4192dd477395b50c014cdc1a1ac572d7c27e2207fa \
+    --hash=sha256:8499d9dd1459dc0d0fe68db0832c3d5fc1361ae8e13d05e6849b358dc3f2c279 \
+    --hash=sha256:866ada14a95b083dd727a845a764cf95dd13ba3dc69a16b99038001b05439709 \
+    --hash=sha256:87069cf875f0262a6e3187ab0f419f5b4280d3dcf4811ef9613c605f6e4dca95 \
+    --hash=sha256:93378f3d14fff07572392ce6a6a2ceb3a1f237733bd6dcb9eb6a2b29b0d19085 \
+    --hash=sha256:95c2d250074cfa76715d58830579c64dff7354484b284c2b8b87e5a38321672c \
+    --hash=sha256:ab5875facfdef77e0a47d5fd39ea178b58e60e454a4c85aa1e52fcb80db7babf \
+    --hash=sha256:b0e0aeb061a1d7dcd2ed59ea57ee56c9b23dd60100825f98238c06ee5cc4467e \
+    --hash=sha256:b78a35c5c74d336f42f44106174b9851c783184a85a3fe3e68857259b37b9ffb \
+    --hash=sha256:c9e04d7e9b03a8a6ac2045f7c5ef741be86727d8f49c45db45f244bdd2bcff17 \
+    --hash=sha256:ca36e7d9430f7481fc7d11e015ae16fbd5575615a8e9060538104778be84addf \
+    --hash=sha256:ceebc3c4f6a109777c0053dfa0282fddb8893eddfb0d598574acfb734a926168 \
+    --hash=sha256:e2c036492e673aad1b7b0d0ccdc0cb30a968353d2c4bf92ac8e73509e1bf212c \
+    --hash=sha256:eb326658f9b73c07081300daba90a8746543b5ea177184daed26528273157294 \
+    --hash=sha256:eb7ae2c4dbdb3c9247e07acc532f91077ae6dbc40ad5bd5dca0bb5a176ee9bda \
+    --hash=sha256:edad1cf5b2ce1912c4d8ddad20e11d333165552aba262c882e28c78bbc09dbf6 \
+    --hash=sha256:eef93a446114ac0193a7b714ce67659db80caf940f3232bad63f4c7a81bc18df \
+    --hash=sha256:f7eaea089345a35130bc9a39b89ec1ff69c208efa97b3f8b25ea5d4c41d88094 \
+    --hash=sha256:f99d206db1f1ae735a8192ab93bd6028f3a42f6fa08467d37a14eb96c9dd34a3
+    # via -r tools/python/requirements.txt
+six==1.16.0 \
+    --hash=sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926 \
+    --hash=sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254
+    # via python-dateutil
diff --git a/tools/python/requirements.txt b/tools/python/requirements.txt
new file mode 100644
index 0000000..7bb0cc1
--- /dev/null
+++ b/tools/python/requirements.txt
@@ -0,0 +1,5 @@
+# After updating this file, run:
+# $ bazel run //tools/python:requirements.update
+matplotlib
+numpy
+scipy
diff --git a/tools/python/runtime_binary.sh b/tools/python/runtime_binary.sh
index a36f085..1a4b3dc 100755
--- a/tools/python/runtime_binary.sh
+++ b/tools/python/runtime_binary.sh
@@ -19,22 +19,26 @@
 # example in a genrule the Python runtime is in the runfiles folder of the
 # tool, not of the genrule.
 # TODO(philipp): Is there a better way to do this?
-BASE_PATH=""
+PYTHON_BIN=""
 for path in ${PYTHONPATH//:/ }; do
-  if [[ "$path" == *.runfiles/python_repo ]]; then
-    BASE_PATH="$path"
-    export LD_LIBRARY_PATH="$path"/lib/x86_64-linux-gnu:"$path"/usr/lib:"$path"/usr/lib/x86_64-linux-gnu:"$path"/../matplotlib_repo/usr/lib
+  if [[ "$path" == *.runfiles/python3_9_x86_64-unknown-linux-gnu ]]; then
+    PYTHON_BIN="$path"/bin/python3
+    export LD_LIBRARY_PATH="$path"/lib
+    break
+  elif [[ "$path" == *.runfiles/python_repo ]]; then
+    PYTHON_BIN="$path"/usr/bin/python3
+    LD_LIBRARY_PATH="${path}/lib/x86_64-linux-gnu:${path}/usr/lib:${path}/usr/lib/x86_64-linux-gnu:${path}/../matplotlib_repo/usr/lib"
+    LD_LIBRARY_PATH+=":${path}/usr/lib/lapack:${path}/usr/lib/libblas:${path}/../matplotlib_repo/rpathed3/usr/lib:${path}/usr/lib/x86_64-linux-gnu/lapack:${path}/usr/lib/x86_64-linux-gnu/blas"
+    export LD_LIBRARY_PATH
     break
   fi
 done
 
-if [[ -z "$BASE_PATH" ]]; then
+if [[ -z "$PYTHON_BIN" ]]; then
   echo "Could not find Python base path." >&2
   echo "More sophisticated logic may be needed." >&2
   exit 1
 fi
 
-export LD_LIBRARY_PATH="${BASE_PATH}/usr/lib/lapack:${BASE_PATH}/usr/lib/libblas:${BASE_PATH}/usr/lib/x86_64-linux-gnu:${BASE_PATH}/../matplotlib_repo/rpathed3/usr/lib:${BASE_PATH}/usr/lib/x86_64-linux-gnu/lapack:${BASE_PATH}/usr/lib/x86_64-linux-gnu/blas"
-
 # Prevent Python from importing the host's installed packages.
-exec "$BASE_PATH"/usr/bin/python3 -sS "$@"
+exec "$PYTHON_BIN" -sS "$@"