diff --git a/commitlint.config.js b/commitlint.config.js
new file mode 100644
index 0000000000000000000000000000000000000000..fdaedd472268225f0927a079164b0e5539743357
--- /dev/null
+++ b/commitlint.config.js
@@ -0,0 +1,9 @@
+module.exports = {
+  extends: ['@commitlint/config-conventional'],
+  rules: {
+    'scope-empty': [2, 'never'],
+    'footer-max-line-length': [0, 'never'],
+    'body-max-line-length': [0, 'never'],
+  },
+  ignores: [(commit) => commit.startsWith('revert:')]
+};
diff --git a/imperative/README.md b/imperative/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..d6dcfdbcd10862432991e1335e2abc580694837e
--- /dev/null
+++ b/imperative/README.md
@@ -0,0 +1,99 @@
+## Build
+
+Same as [MegEngine](/README.md) except passing the additional flag "-DMGE_BUILD_IMPERATIVE_RT=ON" to cmake configure command.
+
+## Test
+
+1. Make sure `make develop` is executed
+
+2. Setup `PYTHONPATH`
+
+   ```bash
+   export PYTHONPATH="$(git rev-parse --show-toplevel)/imperative/python"
+   ```
+3. Run `pytest` (pip install as needed)
+
+   ```bash
+   cd $(git rev-parse --show-toplevel)/imperative/python/test
+   pytest
+   ```
+
+## Concepts
+
+### Op and Tensor-like
+
+An op is a subclass of `OpBase` representing some operation, for example
+
+* `Elemwise`
+* `Reduce`
+
+Op can be parametrized. For example, `Elemwise` has a single parameter `mode`, which is required by its constructor.
+
+A tensor-like is a subclass of `TensorBase` that defines how ops should apply on it, for example
+
+* `RawTensor` launch kernel associated with op
+* `Tracer` record information for autodiff
+
+Op instances are callable with signature `(*args: TensorBase) -> Tuple[TensorBase]`. It will invoke the correct implementation for that specific op and tensor-like, e.g. launch kernel if `args` is `RawTensor`, record information for autodiff if `args` is `Tracer`.
+
+### The `Const` Op
+
+The `Const` op is a special op that is used to convert literal to tensor-likes. Although it does not really use any input, at least one should be provided, otherwise it can't know which specific tensor-like to return.
+
+### Tensor Wrapper
+
+Tensor-likes have a dataflow semantic, thus immutable. `TensorWrapper` provide a mutable layer on top of tensor-likes by replacing the wrapped tensor-like on demand.
+
+## How to Wrap a MegBrain Op
+
+1. Define the op
+
+   Most ops have been automatically generated in `ops.builtin` using `.oprdecl` files (take a look at [basic_arith.oprdecl](/src/opr/impl/basic_arith.oprdecl)). If your op is already there, skip to next step.
+
+   For other ops, this work can still be done automatically with the help of an Python op serializer that matches MegBrain's own.
+
+   Before proceeding, if you are unfamiliar with MegBrain's serializer, here is a brief introduction. Each MegBrain op has a registered name, which is found at `MGB_SEREG_OPR(this_is_the_name, ...)` in some `.sereg.h` file. The default serializer simply write the memory of struct returned by `opr->param()`.
+
+   You can create a serializer by subclassing `ops._internal.helper.OpDef` as follows
+
+   ```python
+   class WhateverDef(OpDef): # must end with "Def"
+       name = 'Whatever' # name in MegBrain serialization registry
+       param_names = ('param',) # Does not have to be 'param', but it is a good practice to mirror
+                                # C++ name, which is usually param(). It can also contain more
+                                # than one element, for example if the C++ serializer writes
+                                # `opr->param1()` followed by `opr->param2()`, you should use
+                                # ('param1', 'param2') instead.
+
+       class Param:
+           def serialize(self):
+               c_struct_memory = bytes(...) # memory of a C++ `Param` struct
+               return b'\x00'*4 + c_struct_memory # remember to add 4 leading bytes
+
+       def __init__(self):
+           self.param = self.Param(...) # must assign to attribute(s) specified in param_names
+   ```
+
+   A concrete example can be found at `ops._internal.misc_ops.DimshuffleDef`.
+
+   Lastly, make sure it is imported in `ops._internal.all_ops` and a corresponding op will show up in `ops.builtin`
+
+2. Define a convenience function
+
+   Use `functional` as a reference.
+
+   Tips:
+
+   * an op instance has to be constructed before applying it
+
+      `op = WhateverOp(param=...)`
+
+   * apply an op by calling the op instance
+
+      `outputs = op(*inputs)`
+
+   * op always return a tuple
+
+      `result, = outputs`
+
+   * input can be any tensor-like
diff --git a/imperative/python/scripts/format.sh b/imperative/python/scripts/format.sh
index 022206559608f30552ced18c7ac284b2b1dfc326..9bce829b153d16dac400b5c1f3d1eaaee35ddb5c 100755
--- a/imperative/python/scripts/format.sh
+++ b/imperative/python/scripts/format.sh
@@ -16,7 +16,11 @@ while getopts 'd' OPT; do
     esac
 done
 
+directories=(megengine test)
+if [[ -d examples ]]; then
+    directories+=(examples)
+fi
 # do not isort megengine/__init__.py file, caused we must
 # init library load path before load dependent lib in core
-isort $ISORT_ARG -j $(nproc) -rc megengine test examples -s megengine/__init__.py
-black $BLACK_ARG --target-version=py35 -- megengine test examples
+isort $ISORT_ARG -j $(nproc) -rc "${directories[@]}" -s megengine/__init__.py
+black $BLACK_ARG --target-version=py35 -- "${directories[@]}"
diff --git a/imperative/python/setup.cfg b/imperative/python/setup.cfg
new file mode 100644
index 0000000000000000000000000000000000000000..186a3f53a7cdbc7986660ed8271f27a126f89f04
--- /dev/null
+++ b/imperative/python/setup.cfg
@@ -0,0 +1,12 @@
+[isort]
+multi_line_output = 3
+include_trailing_comma = true
+force_grid_wrap = 0
+use_parentheses = true
+line_length = 88
+known_first_party = megbrain, megengine
+sections = FUTURE,STDLIB,THIRDPARTY,FIRSTPARTY,LOCALFOLDER
+default_section=THIRDPARTY
+
+[tool:pytest]
+norecursedirs=test/helpers