---
title: "Use the Notebook (Corridor Python Package)"
description: "Work with registered objects from a Notebook using the corridor Python package."
---

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    </svg>
    <span style="font-size: 11px; font-weight: 500; letter-spacing: 0.05em; text-transform: uppercase; color: var(--corridor-purple);">TL;DR</span>
  </div>
  <div style="font-size: 13px; color: var(--sl-color-white); line-height: 1.65;">
    The <strong>Notebook</strong> is a hosted Jupyter environment inside Corridor (Model &rarr; Notebook). It comes with the <code>corridor</code> Python package, which lets you <code>import corridor</code> and work with registered objects (Data Elements, Features, Models, Policies, and more) from code.
  </div>
</div>

## What is it?

The **Notebook** is a hosted JupyterLab environment built into Corridor, under **Model &rarr; Notebook**. It is where you build and experiment in Python without leaving the platform, and it ships with the **`corridor` Python package** already installed and authenticated.

The `corridor` package lets you work with your platform objects (Data Elements, Features, Models, and more) from Python instead of a form: query registered objects and their metadata, read the results of jobs run on the platform, and declare and run new objects on data before registering them back.

## Setup

Inside the Corridor Notebook, the package is pre-configured, so you can import it right away:

```python
# import only what you need
import corridor
from corridor import Feature, DataElement, Model, Policy, create_data

# or pull in everything at once
from corridor import *
```

To switch the workspace you are working in, call `set_workspace`:

```python
from corridor import set_workspace

set_workspace('Fair Lending Team')
```

:::note[Running outside Corridor]
The package can also run in an external Jupyter or Python environment. Set these environment variables before importing `corridor` so it can reach your platform:

- `CORRIDOR_API_URL` - your Corridor API URL.
- `CORRIDOR_API_KEY` - your API key.
- `CORRIDOR_WORKSPACE` - the workspace to work in (defaults to `corridor`).

Inside the Corridor Notebook these are set for you.
:::

## What you can access

Every registered object type has a class in the package. Import the ones you need from `corridor`:

<table class="attr-table">
  <thead>
    <tr><th>Object type</th><th>Fetch by</th><th>What it represents</th></tr>
  </thead>
  <tbody>
    <tr><td class="field-cell"><code>DataTable</code></td><td><code>alias</code> / <code>name</code></td><td>A registered raw data table.</td></tr>
    <tr><td class="field-cell"><code>DataElement</code></td><td><code>alias</code></td><td>A column-backed or aggregated Data Element.</td></tr>
    <tr><td class="field-cell"><code>Feature</code></td><td><code>alias</code></td><td>A derived Feature.</td></tr>
    <tr><td class="field-cell"><code>Model</code></td><td><code>alias</code></td><td>A registered Model and its output.</td></tr>
    <tr><td class="field-cell"><code>ModelTransform</code></td><td><code>model</code> + <code>alias</code></td><td>A transform attached to a Model.</td></tr>
    <tr><td class="field-cell"><code>Policy</code></td><td><code>name</code></td><td>A decision Policy and its workflow blocks.</td></tr>
    <tr><td class="field-cell"><code>GlobalFunction</code></td><td><code>alias</code></td><td>A reusable function, callable from Python.</td></tr>
    <tr><td class="field-cell"><code>GlobalVariable</code></td><td><code>alias</code></td><td>A registered global variable.</td></tr>
    <tr><td class="field-cell"><code>RuntimeParameter</code></td><td><code>alias</code></td><td>A runtime parameter.</td></tr>
    <tr><td class="field-cell"><code>ReasonCode</code></td><td><code>alias</code> / <code>name</code></td><td>A reason code attached to a Model or rule.</td></tr>
    <tr><td class="field-cell"><code>Report</code></td><td><code>name</code></td><td>A report template and its outputs.</td></tr>
    <tr><td class="field-cell"><code>Dataset</code></td><td><code>alias</code></td><td>A registered dataset.</td></tr>
    <tr><td class="field-cell"><code>Framework</code> / <code>Product</code></td><td><code>name</code></td><td>Valuation frameworks and products.</td></tr>
    <tr><td class="field-cell"><code>QualityCheck</code></td><td><code>name</code></td><td>A data quality check.</td></tr>
    <tr><td class="field-cell"><code>MonitoringDashboard</code></td><td>filters</td><td>A monitoring dashboard.</td></tr>
    <tr><td class="field-cell"><code>Entity</code> / <code>TableKey</code></td><td><code>name</code></td><td>Platform entities and their keys.</td></tr>
    <tr><td class="field-cell"><code>User</code></td><td><code>username</code></td><td>A registered platform user.</td></tr>
  </tbody>
</table>

Alongside the classes, a few helper functions let you move data in and out of the package:

- `create_data(...)` - run one or more registered objects on data and get back a DataFrame.
- `get_object_by_alias(...)` - fetch an object when you do not know its type.
- `sync(...)` - push a locally declared object to the platform.

## Find registered objects

Every registry object type is searched and fetched the same way, so the patterns below apply to `Feature`, `DataElement`, `Model`, `Policy`, `Dataset`, and the rest.

### List objects with `.all()`

`.all()` returns a list of objects, optionally filtered:

```python
from corridor import Feature

# every Feature
all_features = Feature.all()

# filter by status, type, keyword, group, permissible purpose, entity, ...
approved  = Feature.all(status='Approved')
numerical = Feature.all(type='Numerical')
income    = Feature.all(contains='income')
```

Any filter takes a single value or a list, for example `Feature.all(type=['Numerical', 'String'])`. The filters accepted are:

- Every class accepts `id`, `alias`, `name`, `contains` (free-text search), and `group`.
- `Feature`, `DataElement`, and `Model` also accept `status`, `type`, `keyword`, `permissible_purpose`, and `platform_entity`.
- `Model` additionally accepts `algorithm_type`.

For a `Model`, `type` and `algorithm_type` are different filters. `type` is the model's **output data type** - `'Numerical'`, `'String'`, `'DateTime'`, or `'Boolean'`. `algorithm_type` is the **kind of model** - `'Binary Classification'`, `'Regression'`, `'Time Series'`, or `'Survival'`. They are independent: a Binary Classification model usually has a `'Numerical'` output (a probability).

```python
from corridor import Model

# probability-output models trained as binary classifiers
Model.all(type='Numerical', algorithm_type='Binary Classification')
```

:::tip[Discovering valid filter values]
If you are not sure what a filter accepts, pass any value - the error message lists the valid ones. For example, `Feature.all(status='garbage')` reports the allowed statuses.
:::

`Policy.all()` is the one exception: it returns a dictionary keyed by policy type, so you index into it by type.

```python
from corridor import Policy

policies = Policy.all()
underwriting = policies['UnderWriting']   # list of UnderWriting policies
```

### Fetch one object

Pass the alias (or name, for `Policy` and `Report`) to the class. Without a version, you get the latest approved (current) version; pass `version=` for a specific one.

```python
from corridor import Feature, Model, Policy

dti      = Feature('debt_to_income')
model    = Model('default_prob')            # Model is fetched by alias
model_v1 = Model('default_prob', version=1)
policy   = Policy('Optimized Return Policy') # Policy is fetched by name
```

If you do not know an object's type, use `get_object_by_alias`:

```python
from corridor import get_object_by_alias

obj = get_object_by_alias('annual_income')  # returns a Feature, DataElement, Model, ...
```

:::note[Fetching a Model]
`Model` is fetched by its **alias**. Passing a model **name** still works for backward compatibility, but it prints a deprecation warning - use the alias going forward.
:::

## Read metadata

Once you have an object, read its attributes directly. The set below is common to `DataElement`, `Feature`, and `Model`:

```python
feature = Feature('debt_to_income')

# not sure what an object exposes? ask it:
help(feature)   # or feature? in Jupyter - lists every attribute with a description
dir(feature)    # the attribute and method names

feature.name                 # 'Debt to Income'
feature.alias                # 'debt_to_income'
feature.version              # 1
feature.type                 # 'Numerical'
feature.is_aggregated        # False
feature.current_status       # 'Approved'
feature.platform_entity      # <Entity name="Applicant">
feature.permissible_purpose  # ['Underwriting']
feature.group                # 'Financial'
feature.description          # the registered description
feature.definition           # the definition code (or None)
feature.inputs               # the objects that flow into it
feature.created_by           # 'analyst'
feature.created_date         # datetime
```

`Model` adds model-specific attributes:

```python
model = Model('default_prob')

model.alias             # 'default_prob'
model.algorithm_type    # 'Binary Classification'
model.input_type        # how the model was defined - 'python function', 'PMML', ...
model.type              # the output type - 'Numerical', ...
model.dependent_variable
model.reason_codes      # reason codes by input, when configured
```

### Approval history

Objects that go through approval expose their review state:

```python
model = Model('default_prob')

model.current_status       # 'Approved'
model.approval_statuses    # per-responsibility review records (None if no approval workflow)
model.approval_histories   # the full audit trail

for status in model.approval_statuses:
    print(status.responsibility, status.status, status.reviewers)
```

## Access raw data

Read the data behind a registered `DataTable` with `to_spark()`:

```python
from corridor import DataTable

loans = DataTable('application')

loans.columns          # the DataColumn objects
loans.dtypes           # {column_alias: column_type, ...}
loans.location         # where the data lives
loans.is_primary       # is this a primary table

df = loans.to_spark()  # a PySpark DataFrame
df.select('int_rate', 'loan_amnt').limit(5).show()
```

For external data, read it with native Spark - point a Spark session at the location:

```python
import pyspark
spark = pyspark.sql.SparkSession.builder.getOrCreate()

application_table = spark.read.parquet('s3a://corridor.dev/master/sampleAppData.parquet')
application_table.limit(5).toPandas()
```

## Work with Policies

A `Policy` exposes its decision workflow as blocks. Each block may contain segments, and each segment contains rules:

```python
from corridor import Policy

policy = Policy('UW Policy with PD Model and Framework')

policy.type               # 'UnderWriting'
policy.strategies         # the decision blocks in the policy
policy.derived_variables  # derived-variable blocks
policy.decision_workflow  # every block (strategies + derived variables), in order
policy.product            # the Product used
```

A block prints with its type, for example:

```python
policy.strategies
# [<ApplicationDecisionBlock name="Eligibility and Risk Gate">,
#  <ApplicationDecisionBlock name="Credit Capacity Gate">,
#  <ApplicationDecisionBlock name="Final Approval Gate">]
```

Walk down from blocks to segments to rules. Not every block is split into segments: when a block has no segmentation, `block.segments` comes back as `None` rather than an empty list. The simplest way to reach every rule in a block is `block.rules`, which returns them all whether the block is segmented or not:

```python
for block in policy.strategies:
    print(f'block: {block.name}')
    for rule in block.rules:          # all rules in the block, segmented or not
        print(f'  rule: {rule.name}')
        print(f'    condition: {rule.definition}')   # the rule's condition tree
```

If you do want to walk segment by segment, guard for the `None` case:

```python
for block in policy.strategies:
    if block.segments:                # None when the block is not segmented
        for segment in block.segments:
            print(segment.name, [rule.name for rule in segment.rules])
```

Each rule's condition is on `rule.definition` - a parsed condition tree of operators and operands, not a plain string. Other useful rule attributes are `rule.name`, `rule.colname` (its column in job output), `rule.actions`, and `rule.reason_codes`.

## Use Global Functions

A `GlobalFunction` is callable straight from Python once you have fetched it:

```python
from corridor import GlobalFunction

# search for one
GlobalFunction.all(contains='exponent')

gf = GlobalFunction('exponential_function_with_rounding')

gf.type         # the return type
gf.arguments    # [InputArgument(alias='base', ...), InputArgument(alias='power', ...)]
gf.definition   # the function body

# call it like any Python function
gf(9, 0.5)      # 3.0
```

To apply a Global Function across a Spark DataFrame, turn it into a UDF with `get_python_function()`:

```python
import pyspark.sql.functions as F
from pyspark.sql.types import FloatType
from corridor import create_data

# start with a DataFrame that has the 'annual_income' column
data = create_data('annual_income')
# add the second argument the function needs, as a constant column
data = data.withColumn('scaling_factor', F.lit(0.95))

# wrap the Global Function as a Spark UDF, declaring its return type
gf_udf = F.udf(gf.get_python_function(), FloatType())
# apply it row-by-row, passing the two columns as arguments
data = data.withColumn('scaled_income', gf_udf('annual_income', 'scaling_factor'))
data.show(5)
```

## Read job results

Jobs (simulations and what-if analyses) are **created and run on the platform**, not from the package - there is no method to trigger one from Python. What the package gives you is read access to jobs that have already run, so you can pull their results, logs, and reports into the Notebook.

Objects that support jobs - `Model`, `Feature`, `DataElement`, `Policy`, `Dataset`, `QualityCheck` - expose the same job surface:

```python
model = Model('default_prob')

model.jobs                 # names of every job run on this Model
job = model.get_job('My Simulation')  # fetch one job by name
model.default_simulation   # the simulation marked as default for this Model (else None)
```

`default_simulation` returns the one simulation the platform has flagged as this object's default - the same one the UI treats as its primary simulation - or `None` if none is set.

### Job status and timing

```python
job.status      # SCHEDULED | QUEUED | COMPILING | RUNNING | COMPLETED | FAILED
job.job_type    # Simulation | What-If Analysis | ...
job.runtime     # a timedelta - how long the job took (None if it has not run)
job.logs        # the execution logs as text (None if none attached)
job.is_old      # True if a newer job supersedes this one
```

### Job configuration

Read back exactly how the job was set up:

```python
job.sample_size           # the sample size, or ratio, the job ran on
job.date_filter           # the date field used to filter, if any
job.date_filter_from_date # start of the date filter
job.date_filter_to_date   # end of the date filter
job.runtime_parameters    # {rtp_alias: {proxy_type: value}} supplied to the job
job.dependencies          # global-variable / product-config values supplied to the job
job.report_versions       # the Report objects attached to the job
job.parameters            # the report parameters the job ran with
```

### Load a job's output data

The quickest way to pull a job's output into the Notebook is to let the platform write the snippet for you. Open the job on any object that has one, go to the **Job Results** tab, and in the **Output Data** panel click **`</> Code`**. Choose:

- **Pandas** or **Spark** - which kind of DataFrame you want.
- **All**, **Inputs Only**, or **Outputs Only** - which columns to load.

The panel generates a ready-to-run snippet that reads the job's result file, for example:

```python
import pandas as pd
result_current = pd.read_parquet("/opt/corridor/data/results/sim_SIM_MODEL_235_job_1440_ent_1_simplified_data.parquet")
```

Copy it straight into a Notebook cell and run it - `result_current` is your job output as a DataFrame.

### Job results and reports from code

You can also reach a job's output programmatically. A job exposes its computed **results** and its rendered **reports**.

```python
job.results          # the computed result data, keyed by entity label then output alias
job.report_dashboard # the rendered reports (see below)
```

`job.results` only works for a completed job that actually produced result data, such as a simulation. On a job that has no results to parse - one that has not finished, or a report-only job - it raises an error instead of returning empty. If you hit an error here, use the **`</> Code`** snippet above, or check that the job is `COMPLETED` and is the kind of job that produces results.

`job.report_dashboard` returns the job's reports grouped by the report group they belong to, as a nested dictionary of `{group_name: {report_name: JobReport}}` (or `None` if the job has no reports). Printed, it looks like this:

```python
job.report_dashboard
# OrderedDict([
#   ('Corridor Model Output Summary Statistics',
#     OrderedDict([('Summary Statistics', <JobReport #134 name="Summary Statistics">)])),
#   ('Corridor Model Output Histogram',
#     OrderedDict([('Histogram', <JobReport #137 name="Histogram">)])),
#   ...
# ])
```

Index in with the group name then the report name to get a single `JobReport`, which you can render inline in the Notebook:

```python
report = job.report_dashboard['Corridor Model Output Histogram']['Histogram']

report.name         # the report's name
report.status       # COMPLETED | ...
report.report_type  # Figure | Downloadable File | Metric
report.raw_data     # renders inline: a Plotly figure, DataFrame, PDF, image, or Markdown
report.logs         # logs attached to this report
```

### What-if jobs

A what-if job references the objects and baseline it was run against:

```python
job.reused_job_object   # the object used for Existing Job Results
job.reused_job          # the specific job that was reused
job.baseline_job        # the baseline job this what-if compares against (else None)
```

For a Policy what-if job, you can also reach the what-if policy version and resolve a block, segment, or rule from its column name in the job output:

```python
policy_job = Policy('My Policy').get_job('What-If Run')
policy_job.whatif_policy   # the what-if Policy version being tested

# resolve a column like 'block-1', 'segment-1.2', or 'rule-1.1.3' to its registered object
rule = policy_job.get_registered_object_by_colname('rule-1.1.2', 'current')
rule.name
```

## Run objects on data

`create_data(...)` runs one or more registered objects and returns a DataFrame with the results. Use it to test a definition before or after you register it.

Most of the time you just name the object. `create_data` looks up which tables it reads, finds those tables on the platform, and loads them for you:

```python
from corridor import create_data

output = create_data('debt_to_income')
```

Pass `data` only when you want to supply the tables yourself, such as test data. When you do, give it every table the object reads. The key for each table is the table's registered alias (the alias it has on the platform), and the value is your DataFrame:

```python
output = create_data(
    'debt_to_income',
    data={'application': application_df},     # key = the table's registered alias
    runtime_params={'default_months': 12},    # values for any runtime parameters
)
```

If you pass `data` but leave out a table the object needs, `create_data` stops and tells you which table is missing. The data you pass is used instead of the platform's, so it does not read the registered tables in this case.

You can pass Feature, Data Element, Model, or Policy aliases (or the objects themselves). A Policy runs on its own: you cannot mix it with other objects, and only one Policy is allowed per call.

## Register/Sync your work back to the platform

Building an object is two steps: **declare** it in Python, then **`sync`** it to the platform. `sync` creates the object if it is new, or updates your Draft version if it already exists.

### Declare an object

Use the `.declare(...)` decorator (or classmethod) to define a new object. `Feature`, `Model`, `GlobalFunction`, and `Report` wrap a **function** whose body becomes the definition; `DataElement` and `DataTable` wrap a **Spark DataFrame**, since they describe existing columns rather than computed logic.

The function-based forms need one thing the DataFrame-based forms do not: an anchor comment.

- **Feature, Model, Global Function, Report** (function-based): the body must contain the line `# -- BEGIN DEFINITION --`. Everything above it (the signature and docstring) is discarded; everything below it becomes the definition registered on the platform.</br>
Leave it out and `sync` fails with `Expected anchor comment # -- BEGIN DEFINITION --`.
- **Data Element, Data Table** (DataFrame-based): no anchor needed.

**Declare a Feature** from a function. Each argument is resolved to a registered input by its alias, exactly like the **Input** section of the form:

```python
from corridor import Feature

@Feature.declare(entity='Applicant', name='Debt to Income', group='Financial')
def debt_to_income(annual_income, monthly_debt) -> float:
    """Ratio of monthly debt to annual income."""
    # -- BEGIN DEFINITION --
    return (monthly_debt * 12) / annual_income
```

**Declare a Data Element** from a column of a Spark DataFrame (the DataFrame must itself come from `DataTable.declare()`):

```python
from corridor import DataElement

annual_income = DataElement.declare(
    table=applicant_df,        # a DataFrame from DataTable.declare()
    column='annual_income',    # the column to register
    group='Financial',
)
```

**Declare a Data Table** to register a raw table at a `location`:

```python
from corridor import DataTable

application = DataTable.declare(
    location='s3a://corridor.dev/master/application.parquet',
    alias='application',
    table=application_df,      # a Spark DataFrame whose schema defines the columns
)
```

**Declare a Model** with `.declare(...)`, then attach its scoring function. Note that `type` takes a **Python type** (like `float`), not a string - `sync` maps it to the platform data type:

```python
from corridor import Model

model = Model.declare(
    alias='default_prob',
    entity='Applicant',
    algorithm_type='Binary Classification',  # the kind of model
    type=float,                              # a Python type -> 'Numerical'
    input_type='python function',
)

@model.model_function()
def score(annual_income, debt_to_income) -> float:
    # -- BEGIN DEFINITION --
    ...
```

### Sync the declared object

```python
from corridor import sync

sync(debt_to_income)                          # prompts for confirmation
sync(debt_to_income, skip_confirmation=True)  # push without prompting
```

`sync` supports these declared types: **Global Function, Global Variable, Runtime Parameter, Report, Data Table, Data Element, Feature, and Model** (a Model also syncs its transforms). Datasets, Frameworks, and Policies cannot be synced.

**What `sync` reads from your declaration.** What you write in Python becomes the registered definition:

- The **function name** becomes the **alias** (and the name, unless you passed one to `.declare`).
- The **docstring** becomes the **description**.
- The **return type annotation** becomes the **data type**.
- The **function body below the anchor** becomes the **definition**.
- Any **registered object referenced inside the body** is picked up as an input - and if that input was also declared locally, it is synced first, automatically.

**Values the declare parameters accept:**

<table class="attr-table">
  <thead>
    <tr><th>Parameter</th><th>On</th><th>Accepts</th></tr>
  </thead>
  <tbody>
    <tr><td class="field-cell"><code>algorithm_type</code></td><td>Model</td><td><code>'Binary Classification'</code>, <code>'Regression'</code>, <code>'Time Series'</code>, or <code>'Survival'</code></td></tr>
    <tr><td class="field-cell"><code>type</code></td><td>Model, Global Variable, Runtime Parameter</td><td>a Python type (see the mapping below)</td></tr>
    <tr><td class="field-cell"><code>input_type</code></td><td>Model</td><td><code>'python function'</code> (attach a <code>@model.model_function()</code>) or <code>'custom'</code> (attach <code>@model.init</code> and <code>@model.run</code>)</td></tr>
    <tr><td class="field-cell"><code>entity</code></td><td>Feature, Model</td><td>the name of a registered platform Entity (e.g. <code>'Applicant'</code>)</td></tr>
    <tr><td class="field-cell"><code>permissible_purpose</code></td><td>Feature, DataElement, Model</td><td>a list of permissible-purpose tag names; omit to use all</td></tr>
    <tr><td class="field-cell"><code>group</code></td><td>all</td><td>any group name; omit to use <code>'Default'</code></td></tr>
  </tbody>
</table>

`sync` maps the Python type you pass as `type` to a platform data type:

| Python type | Data type |
| --- | --- |
| `float`, `int` | Numerical |
| `str` | String |
| `bool` | Boolean |
| `datetime.datetime` | DateTime |
| `list[...]` | the matching Array type |

**The confirmation flow.** `sync` compares your declaration against the platform, prints a git-style diff of what will change, then asks before writing:

```
Creating new Feature 'debt_to_income' with values:
[Alias]
	+ debt_to_income
[Definition]
	+ return (monthly_debt * 12) / annual_income
...
Confirm pushing changes to platform? [y/N]:
```

Answer `y` to push, anything else to cancel. If your declaration already matches the platform, it prints `Feature 'debt_to_income' up to date with platform` and does nothing. Pass `skip_confirmation=True` to push without the prompt - useful in scripted runs.

:::note[Which version sync updates]
`sync` updates your **Draft** version, since that is the only directly editable one. If no Draft exists it falls back to the current version. Send the object for [approval](/user-guide/how-tos/approve-an-object/) once you are happy with it.
:::

## Share draft objects

Share a draft object with other users or roles before it is approved, without leaving the Notebook:

```python
de = DataElement('annual_income')

de.grant_share_for_user('analyst', access_type='Write')
de.grant_share_for_role('Underwriting', access_type='Read')

de.user_accesses   # who the object is shared with
de.role_accesses

de.revoke_share_for_user('analyst')
```

## What's Next

- Register the objects you build here through the UI: a [Data Element](/user-guide/how-tos/register-a-data-element/), [Feature](/user-guide/how-tos/register-a-feature/), or [Model](/user-guide/how-tos/register-a-model-definition/).
- [Run a Simulation](/user-guide/how-tos/run-a-simulation/) on a registered object to validate it on a full sample.
- Send your work for [approval](/user-guide/how-tos/approve-an-object/) so it can be used outside your draft workspace.