### Add deadsnakes PPA and install Python versions

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Add the deadsnakes PPA and install multiple Python versions on Ubuntu.

```bash
sudo add-apt-repository -y ppa:deadsnakes
sudo apt-get update
sudo apt-get install python3.{6,7,8,9}
```

--------------------------------

### Show Forward Reference Chain

Source: https://github.com/mgedmin/objgraph/blob/master/docs/chain.md

Visualizes the chain of references from a starting object to an object matching a specific condition. Ensure objgraph is installed and the target object is reachable from the starting object.

```Python
>>> class MyUnpicklableObject(object):
...     def __getstate__(self):
...         raise NotImplementedError
... 
>>> my_object = dict(foo=dict(unrelated='things'),
...                  bar=[dict(nesting='fun'),
...                       dict(boobytrap=MyUnpicklableObject())])
>>> import objgraph
>>> objgraph.show_chain(
...     objgraph.find_ref_chain(
...         my_object,
...         lambda x: isinstance(x, MyUnpicklableObject)),
...     backrefs=False,
...     filename='forward-chain.png')
Graph written to ...dot (4 nodes)
Image generated as forward-chain.png
```

--------------------------------

### Release process command

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Run the make release command to get instructions for making a new release. This command is safe to run anytime.

```bash
make release
```

--------------------------------

### Define a simple Node class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/highlighting.txt

This snippet defines a basic class used to create a graph structure for demonstration purposes. It's a prerequisite for the highlighting example.

```Python
class Node(object):
    def __init__(self, *neighbours):
        self.neighbours = list(neighbours)
a = Node()
b = Node(a)
c = Node(b)
d = Node(c)
a.neighbours.append(d)
```

--------------------------------

### Clone the objgraph repository

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Get the latest source code for objgraph from GitHub.

```bash
git clone https://github.com/mgedmin/objgraph
```

--------------------------------

### Find and Show Reference Chain

Source: https://github.com/mgedmin/objgraph/blob/master/docs/chain.txt

Uses objgraph to find a reference chain from a starting object to an instance of MyUnpicklableObject and generates a PNG image of the chain.

```python
import objgraph
objgraph.show_chain(
    objgraph.find_ref_chain(
        my_object,
        lambda x: isinstance(x, MyUnpicklableObject)),
    backrefs=False,
    filename='forward-chain.png')
```

--------------------------------

### Show Object References

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.txt

Generates a graph of object references starting from specified roots. Useful for debugging memory leaks. Ensure the graphviz 'dot' executable is in your PATH.

```python
objgraph.show_refs(roots[:3], refcounts=True, filename='roots.png')
```

--------------------------------

### Show Most Common Object Types

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.txt

Displays a list of the most common object types currently in memory, along with their counts. Useful for getting a high-level overview of memory usage.

```python
>>> objgraph.show_most_common_types() # doctest: +RANDOM_OUTPUT
    tuple                      5224
    function                   1329
    wrapper_descriptor         967
    dict                       790
    builtin_function_or_method 658
    method_descriptor          340
    weakref                    322
    list                       168
    member_descriptor          167
    type                       163
```

--------------------------------

### Track Object Growth

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.md

Show the growth in object counts since the last call to show_growth or since program start. Useful for identifying newly created objects that might indicate a memory leak. The 'limit' parameter restricts the output to the top N growing types.

```python
>>> objgraph.show_growth(limit=3)
```

```python
>>> computate_something()
>>> objgraph.show_growth()
```

--------------------------------

### Get and Analyze Leaking Objects

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.txt

Retrieves objects that might be leaking memory by identifying objects not properly deallocated. Used in conjunction with show_most_common_types to analyze potential leaks.

```python
>>> roots = objgraph.get_leaking_objects()
>>> len(roots) # doctest: +RANDOM_OUTPUT
    4621
```

```python
>>> objgraph.show_most_common_types(objects=roots)
    ... # doctest: +RANDOM_OUTPUT
    tuple          4333
    dict           171
    list           74
    instancemethod 4
    listiterator   2
    MemoryError    1
    Sub            1
    RuntimeError   1
    Param          1
    Add            1
```

--------------------------------

### Manual restview command for PyPI description

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Manually preview the PyPI long description using restview with a command that executes setup.py.

```bash
restview -e "python setup.py --long-description"
```

--------------------------------

### Clean, build images, and documentation

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Clean previous build artifacts, generate images, and rebuild the documentation.

```bash
make clean images docs
```

--------------------------------

### Preview PyPI long description with restview

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Use a make rule to preview the PyPI long description, which is generated by concatenating README.rst and CHANGES.rst.

```bash
make preview-pypi-description
```

--------------------------------

### Run the test suite

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Execute the test suite to ensure the project is functioning correctly. This primarily checks for crashes.

```bash
make test
```

--------------------------------

### Configure git for imgdiff comparison

Source: https://github.com/mgedmin/objgraph/blob/master/HACKING.rst

Set up git to use imgdiff for comparing PNG files, useful for reviewing documentation image changes.

```bash
git config diff.imgdiff.command 'f() { imgdiff $1 $2; }; f'
git diff docs/*.png
```

--------------------------------

### Activate and Iterate a Generator

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.md

Instantiate the generator and retrieve its first value using next(). This shows how to activate a generator.

```pycon
>>> it = count_to_three()
>>> next(it)
1

```

--------------------------------

### Check Source Tarball Completeness

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Run this command to ensure that source tarballs generated with `python setup.py sdist` are not missing any files. This is automatically performed by `make release`.

```bash
make distcheck
```

--------------------------------

### Configure git for image diffing with options

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Configure git to use imgdiff with specific options for easier visual comparison of image changes.

```bash
git config diff.imgdiff.command 'f() { imgdiff $1 $2; }; f'
```

--------------------------------

### Generate Reference Graph for All Characters

Source: https://github.com/mgedmin/objgraph/blob/master/docs/quoting.txt

Use objgraph.show_refs to create a graph visualizing references for a dictionary containing all 256 possible characters. Set 'too_many' to a value greater than the number of nodes to ensure all are included. The output file is specified by the 'filename' argument.

```python
import objgraph
all_the_chars = dict((chr(i), i) for i in range(256))
objgraph.show_refs(all_the_chars, too_many=600,
                   filename='all-the-chars.dot')
```

--------------------------------

### Run tests with tox for multiple Python versions

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Use tox to run the test suite across all supported Python versions.

```bash
tox -p auto
```

--------------------------------

### Configure git for image diffing

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Configure git to use imgdiff for comparing image differences, useful for debugging test failures.

```bash
git config diff.imgdiff.command 'f() { imgdiff --eog -H $1 $2; }; f'
```

--------------------------------

### View image differences

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

View the differences between generated images using git diff.

```bash
git diff docs/*.png
```

--------------------------------

### Configure git for enhanced imgdiff comparison

Source: https://github.com/mgedmin/objgraph/blob/master/HACKING.rst

Configure git to use imgdiff with specific options (--eog -H) for a more detailed comparison of PNG images.

```bash
git config diff.imgdiff.command 'f() { imgdiff --eog -H $1 $2; }; f'
git diff docs/*.png
```

--------------------------------

### Highlight Node instances in object graph

Source: https://github.com/mgedmin/objgraph/blob/master/docs/highlighting.txt

Use objgraph.show_backrefs to visualize object references and highlight nodes that are instances of the Node class. This helps in understanding the structure of the graph.

```Python
import objgraph
objgraph.show_backrefs(a, max_depth=15,
    extra_ignore=[id(locals())],
    highlight=lambda x: isinstance(x, Node),
    filename='highlight.png') # doctest: +NODES_VARY
```

--------------------------------

### Show Object References

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.txt

Generates a graph of objects reachable from a given set of objects. Useful for visualizing object relationships.

```python
>>> x = []
>>> y = [x, [x], dict(x=x)]
>>> import objgraph
>>> objgraph.show_refs([y], filename='sample-graph.png')
```

--------------------------------

### objgraph.show_growth

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Prints object growth statistics to a file.

```APIDOC
## objgraph.show_growth

### Description
Prints object growth statistics to a file.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **limit** (int, optional) - The maximum number of types to track. Defaults to 10.
- **peak_stats** (dict, optional) - A dictionary to store peak statistics. Defaults to an empty dictionary.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
- **file** (file-like object, optional) - The file to write to. Defaults to sys.stdout.
- **filter** (callable, optional) - A filter function to apply to objects.
```

--------------------------------

### Generate images for visual testing

Source: https://github.com/mgedmin/objgraph/blob/master/HACKING.rst

Create visual representations of object graphs for manual inspection. This is useful for identifying subtle output errors.

```bash
make images
```

--------------------------------

### objgraph.at

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Returns an object at a given memory address.

```APIDOC
## objgraph.at

### Description
Returns an object at a given memory address.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **address** (int) - Required - The memory address of the object.
```

--------------------------------

### objgraph.show_chain

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Displays a reference chain.

```APIDOC
## objgraph.show_chain

### Description
Displays a reference chain.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **chain** (iterable) - Required - The chain of objects to display.
- **highlight** (callable, optional) - A callable to highlight specific objects.
- **filename** (string, optional) - The file to save the graph to.
- **extra_info** (callable, optional) - A callable to add extra information to nodes.
- **refcounts** (bool, optional) - If True, display reference counts. Defaults to False.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
```

--------------------------------

### Visualize Object Reference Chain to Module

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.txt

Generates a graph showing a specific reference chain from a module to a 'Canary' object. This technique is useful for debugging garbage collection issues.

```python
objgraph.show_chain(
    objgraph.find_backref_chain(objgraph.by_type('Canary')[0],
                                objgraph.is_proper_module),
    filename='canary-chain.png')
```

--------------------------------

### Visualize Object Back References

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.txt

Generates a graph visualizing the objects that hold a reference to 'Canary' objects. This is useful for understanding object relationships and memory retention. Requires 'Canary' objects to be present.

```python
objgraph.show_backrefs(objgraph.by_type('Canary'),
                       max_depth=7,
                       filename='canary.png')
```

--------------------------------

### Generate Graph with Highlighted Nodes

Source: https://github.com/mgedmin/objgraph/blob/master/docs/highlighting.md

Generates a back-reference graph, highlighting nodes that are instances of the Node class. This requires the objgraph library to be imported.

```python
import objgraph
>>> objgraph.show_backrefs(a, max_depth=15,
...     extra_ignore=[id(locals())],
...     highlight=lambda x: isinstance(x, Node),
...     filename='highlight.png')
Graph written to ....dot (12 nodes)
Image generated as highlight.png
```

--------------------------------

### objgraph.show_refs

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Displays references for a set of objects.

```APIDOC
## objgraph.show_refs

### Description
Displays references for a set of objects.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **objs** (iterable) - Required - The objects to find references for.
- **max_depth** (int, optional) - The maximum depth to search. Defaults to 3.
- **extra_ignore** (iterable, optional) - An iterable of objects to ignore.
- **filter** (callable, optional) - A filter function to apply.
- **too_many** (int, optional) - The threshold for too many references. Defaults to 10.
- **highlight** (callable, optional) - A callable to highlight specific objects.
- **filename** (string, optional) - The file to save the graph to.
- **extra_info** (callable, optional) - A callable to add extra information to nodes.
- **refcounts** (bool, optional) - If True, display reference counts. Defaults to False.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
```

--------------------------------

### Visualize Reference Chain to Module Root

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.md

Trace and visualize the reference chain from a specific object back to a module root. This is crucial for diagnosing memory leaks by showing what is keeping an object alive. Requires graphviz for image generation.

```python
>>> import random
>>> objgraph.show_chain(
...     objgraph.find_backref_chain(
...         random.choice(objgraph.by_type('MyBigFatObject')),
...         objgraph.is_proper_module),
...     filename='chain.png')
```

--------------------------------

### Define a Custom Class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.md

Define a simple custom class named 'Canary'. This is used to demonstrate object tracking.

```pycon
>>> class Canary(object):
...     pass

```

--------------------------------

### Visualize Object Back-references

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.md

Use objgraph.show_backrefs() to visualize all objects that hold a reference to instances of 'Canary'. This is useful for debugging memory leaks. Specify max_depth and output filename.

```pycon
>>> objgraph.show_backrefs(objgraph.by_type('Canary'),
...                        max_depth=7,
...                        filename='canary.png')
Graph written to ....dot (15 nodes)
Image generated as canary.png

```

--------------------------------

### Define a Custom Class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.txt

Defines a simple custom class named 'Canary'. This is a basic building block for demonstrating object tracking.

```python
class Canary(object):
    pass
```

--------------------------------

### Visualize Reference Chain to a Module

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.md

Use objgraph.show_chain() to visualize a specific reference chain leading from a module to a target object. This helps in understanding garbage collection roots.

```pycon
>>> objgraph.show_chain(
...     objgraph.find_backref_chain(objgraph.by_type('Canary')[0], 
...                                 objgraph.is_proper_module),
...     filename='canary-chain.png')
Graph written to ....dot (11 nodes)
Image generated as canary-chain.png

```

--------------------------------

### Generate HTML test coverage report

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Generate an HTML report for test coverage, which can be browsed in a web browser.

```bash
make coverage
coverage html
```

--------------------------------

### Show Object Backreferences

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.txt

Generates a graph of objects that reference a given set of objects. Helps in understanding what objects are holding onto a specific object.

```python
>>> objgraph.show_backrefs([x], filename='sample-backref-graph.png')
```

--------------------------------

### Show References with All Characters

Source: https://github.com/mgedmin/objgraph/blob/master/docs/quoting.md

Generates a graph of references for a dictionary containing all 256 ASCII characters. Use this to test how quoting handles a wide range of characters. The 'too_many' parameter is set to a high value to ensure all references are included.

```python
>>> import objgraph
>>> all_the_chars = dict((chr(i), i) for i in range(256))
>>> objgraph.show_refs(all_the_chars, too_many=600,
...                    filename='all-the-chars.dot')
Graph written to all-the-chars.dot (... nodes)
```

--------------------------------

### Compare generated images with previous versions

Source: https://github.com/mgedmin/objgraph/blob/master/HACKING.rst

Use imgdiff to visually compare generated PNG images of object graphs. This helps in identifying unintended changes.

```bash
make images PYTHON=pythonX.Y
git config diff.imgdiff.command 'f() { imgdiff --eog -H $1 $2; }; f'
git diff docs/*.png
```

--------------------------------

### objgraph.at_addrs

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Returns objects at a given set of memory addresses.

```APIDOC
## objgraph.at_addrs

### Description
Returns objects at a given set of memory addresses.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **address_set** (set of int) - Required - A set of memory addresses.
```

--------------------------------

### Visualize Backreferences with Reference Counts

Source: https://github.com/mgedmin/objgraph/blob/master/docs/references.md

Enable reference counts in `show_backrefs` to display the number of references to each object. This helps in understanding the exact reference counts, though interpreter internals might add extra references.

```python
>>> import sys
>>> one_reference = object()
>>> objgraph.show_backrefs([one_reference], refcounts=True,
...     filename='refcounts.png')
```

--------------------------------

### objgraph.show_most_common_types

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Prints the most common object types to a file.

```APIDOC
## objgraph.show_most_common_types

### Description
Prints the most common object types to a file.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **limit** (int, optional) - The maximum number of types to print. Defaults to 10.
- **objects** (iterable, optional) - An iterable of objects to consider. If not provided, all objects are considered.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
- **file** (file-like object, optional) - The file to write to. Defaults to sys.stdout.
```

--------------------------------

### Show Object Growth

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.txt

Tracks and displays the increase in object counts between two points in time. Essential for identifying potential memory leaks by observing newly created objects.

```python
>>> objgraph.show_growth(limit=3) # doctest: +RANDOM_OUTPUT
    tuple                  5228     +5228
    function               1330     +1330
    wrapper_descriptor      967      +967
```

```python
>>> computate_something()
>>> objgraph.show_growth() # doctest: +RANDOM_OUTPUT
    MyBigFatObject        2        +2
    dict                797        +1
```

--------------------------------

### Generate images for visual debugging

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Generate images for visual debugging, specifying a Python version. This is useful when tests fail.

```bash
make images PYTHON=pythonX.Y
```

--------------------------------

### Create a Generator Using a Custom Class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.md

Define a generator function that instantiates and uses the custom 'Canary' class. This generator yields numbers.

```pycon
>>> def count_to_three():
...     tweety = Canary()
...     yield 1
...     yield 2
...     yield 3

```

--------------------------------

### Visualizing Classes with Finalizers

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.txt

This code uses `objgraph.show_refs` to visualize the references of a class that defines a `__del__` method. Unlike instances in cycles, the class definition itself is not considered uncollectable garbage.

```python
import objgraph

objgraph.show_refs(Nondestructible, max_depth=1,
                   filename='class-with-finalizers.png')
```

--------------------------------

### Visualize Object References

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.md

Generate a graph of object references for a subset of objects, including reference counts. This is useful for visually debugging complex reference chains and potential leaks.

```python
>>> objgraph.show_refs(roots[:3], refcounts=True, filename='roots.png')
...
Graph written to ...dot (19 nodes)
Image generated as roots.png
```

--------------------------------

### Revert changed image and dot files

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Discard changes to image and dot files in the docs directory.

```bash
git checkout -- docs/*.png docs/*.dot
```

--------------------------------

### Create a Generator Using a Custom Class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.txt

Defines a generator function that instantiates and uses the custom 'Canary' class. It yields numbers from 1 to 3.

```python
def count_to_three():
    tweety = Canary()
    yield 1
    yield 2
    yield 3
```

--------------------------------

### objgraph.growth

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Tracks object growth over time.

```APIDOC
## objgraph.growth

### Description
Tracks object growth over time.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **limit** (int, optional) - The maximum number of types to track. Defaults to 10.
- **peak_stats** (dict, optional) - A dictionary to store peak statistics. Defaults to an empty dictionary.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
- **filter** (callable, optional) - A filter function to apply to objects.
```

--------------------------------

### Visualize classes with __del__ methods using objgraph

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.md

This snippet uses `objgraph.show_refs` to visualize the references originating from a class that defines a `__del__` method, specifically `Nondestructible`. This helps distinguish between instances that are uncollectable and the class definition itself. The output is saved to `class-with-finalizers.png`.

```python
objgraph.show_refs(Nondestructible, max_depth=1,
                   filename='class-with-finalizers.png')
```

--------------------------------

### Visualizing Uncollectable Objects with objgraph

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.txt

This snippet uses `objgraph.show_backrefs` to visualize the back-references of uncollectable objects, specifically highlighting instances of 'Nondestructible'. This helps in understanding why they are not collected.

```python
import objgraph

objgraph.show_backrefs(objgraph.by_type('Nondestructible'),
                       filename='finalizers.png')
```

--------------------------------

### Generate test coverage report

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Generate a test coverage report to identify areas not covered by tests.

```bash
make coverage
```

--------------------------------

### Activate and Iterate a Generator

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.txt

Activates the 'count_to_three' generator and retrieves the first yielded value using next().

```python
it = count_to_three()
next(it)
```

--------------------------------

### objgraph.by_type

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Returns all objects of a given type.

```APIDOC
## objgraph.by_type

### Description
Returns all objects of a given type.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **typename** (string) - Required - The name of the type to filter by.
- **objects** (iterable, optional) - An iterable of objects to consider. If not provided, all objects are considered.
```

--------------------------------

### objgraph.show_backrefs

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Displays back-references for a set of objects.

```APIDOC
## objgraph.show_backrefs

### Description
Displays back-references for a set of objects.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **objs** (iterable) - Required - The objects to find back-references for.
- **max_depth** (int, optional) - The maximum depth to search. Defaults to 3.
- **extra_ignore** (iterable, optional) - An iterable of objects to ignore.
- **filter** (callable, optional) - A filter function to apply.
- **too_many** (int, optional) - The threshold for too many references. Defaults to 10.
- **highlight** (callable, optional) - A callable to highlight specific objects.
- **filename** (string, optional) - The file to save the graph to.
- **extra_info** (callable, optional) - A callable to add extra information to nodes.
- **refcounts** (bool, optional) - If True, display reference counts. Defaults to False.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
```

--------------------------------

### Highlight code coverage in Vim

Source: https://github.com/mgedmin/objgraph/blob/master/docs/HACKING.md

Use a Vim plugin to highlight lines not covered by tests while editing code.

```bash
make coverage
vim objgraph.py
  :HighlightCoverage
```

--------------------------------

### Count Instances of a Custom Class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.txt

Uses objgraph.count() to determine the number of live 'Canary' objects in memory. This helps verify object existence.

```python
import objgraph
objgraph.count('Canary')
```

--------------------------------

### Show Reference Chain to Module

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.txt

Visualizes the chain of references from a garbage collector root (like a module) to a specific object. Helps in debugging memory leaks by tracing object lifecycles.

```python
>>> import random
>>> objgraph.show_chain(
...     objgraph.find_backref_chain(
...         random.choice(objgraph.by_type('MyBigFatObject')),
...         objgraph.is_proper_module),
...     filename='chain.png') # doctest: +NODES_VARY
    Graph written to ...dot (13 nodes)
    Image generated as chain.png
```

--------------------------------

### Adding Object IDs to References

Source: https://github.com/mgedmin/objgraph/blob/master/docs/extra-info.md

Use the `extra_info` parameter in `objgraph.show_refs` to display object IDs. This helps in identifying specific objects within the graph. Ensure `objgraph` is imported.

```python
>>> x = []
>>> y = [x, [x], dict(x=x)]
>>> import objgraph
>>> objgraph.show_refs([y], extra_info=lambda x: hex(id(x)),
...                    filename='extra-info.png')
Graph written to ....dot (... nodes)
Image generated as extra-info.png
```

--------------------------------

### Visualize uncollectable objects with objgraph

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.md

This snippet uses `objgraph.show_backrefs` to visualize the back-references of uncollectable objects of type `Nondestructible`. This helps in understanding the structure of the cycle and why they are uncollectable. The output is saved to `finalizers.png`.

```python
objgraph.show_backrefs(objgraph.by_type('Nondestructible'),
                       filename='finalizers.png')
```

--------------------------------

### Visualize Backreferences with Truncation

Source: https://github.com/mgedmin/objgraph/blob/master/docs/references.md

Use `show_backrefs` to visualize objects pointing to a target object. The `too_many` parameter limits the displayed backreferences, and `max_depth` controls the graph depth.

```python
>>> moo = 'moo'
>>> refs_to_moo = [[moo] for n in range(42)]
>>> objgraph.show_backrefs([moo], too_many=5, max_depth=1, filename='42.png')
```

--------------------------------

### Show Most Common Types of Leaking Objects

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.md

After identifying potential leaking objects, use show_most_common_types to see the distribution of their types. This helps in diagnosing the nature of the leaks.

```python
>>> objgraph.show_most_common_types(objects=roots)
...
tuple          4333
dict           171
list           74
instancemethod 4
listiterator   2
MemoryError    1
Sub            1
RuntimeError   1
Param          1
Add            1
```

--------------------------------

### Identify uncollectable objects using gc.garbage

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.md

After removing all external references to the cyclic objects and running the garbage collector, this snippet shows how to check `gc.garbage` to find the uncollectable objects. It verifies that one such object is present.

```python
import objgraph
del x, y, z
import gc
_ = gc.collect()
len(gc.garbage)
```

--------------------------------

### Define Node Class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/highlighting.md

Defines a simple Node class with a list of neighbours, used for creating a sample object graph.

```python
class Node(object):
    def __init__(self, *neighbours):
        self.neighbours = list(neighbours)
>>> a = Node()
>>> b = Node(a)
>>> c = Node(b)
>>> d = Node(c)
>>> a.neighbours.append(d)
```

--------------------------------

### Looking Up Objects by ID

Source: https://github.com/mgedmin/objgraph/blob/master/docs/extra-info.md

The `objgraph.at()` function allows you to retrieve an object using its ID, which is useful for inspecting objects identified in the graph. This function works for objects tracked by the cyclic garbage collector.

```python
>>> objgraph.at(id(x)) is x
True
```

--------------------------------

### objgraph.typestats

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Returns statistics about object types.

```APIDOC
## objgraph.typestats

### Description
Returns statistics about object types.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **objects** (iterable, optional) - An iterable of objects to consider. If not provided, all objects are considered.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
```

--------------------------------

### Visualize Objects with Too Many References

Source: https://github.com/mgedmin/objgraph/blob/master/docs/references.md

Use `show_refs` to visualize objects with a high number of references. The `too_many` parameter truncates the graph to avoid overwhelming detail.

```python
import objgraph
>>> objgraph.show_refs([list(range(7))], too_many=5, filename='too-many.png')
```

--------------------------------

### Count Instances of a Custom Class

Source: https://github.com/mgedmin/objgraph/blob/master/docs/generator-sample.md

Use objgraph.count() to determine the number of instances of the 'Canary' class currently in memory. This helps in understanding object lifecycle.

```pycon
>>> import objgraph
>>> objgraph.count('Canary')
1

```

--------------------------------

### Add Object IDs to Graph

Source: https://github.com/mgedmin/objgraph/blob/master/docs/extra-info.txt

Use the 'extra_info' parameter to include object IDs in the generated graph. This helps in identifying specific objects later.

```python
>>> x = []
>>> y = [x, [x], dict(x=x)]
>>> import objgraph
>>> objgraph.show_refs([y], extra_info=lambda x: hex(id(x)),
...                    filename='extra-info.png')
```

--------------------------------

### Create a Nested Object Structure

Source: https://github.com/mgedmin/objgraph/blob/master/docs/chain.txt

Creates a complex nested dictionary containing instances of the custom unpicklable object to test reference chain finding.

```python
my_object = dict(foo=dict(unrelated='things'),
                 bar=[dict(nesting='fun'),
                      dict(boobytrap=MyUnpicklableObject())])
```

--------------------------------

### objgraph.get_new_ids

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Retrieves newly created object IDs.

```APIDOC
## objgraph.get_new_ids

### Description
Retrieves newly created object IDs.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **skip_update** (bool, optional) - If True, skip updating the object ID cache. Defaults to False.
- **limit** (int, optional) - The maximum number of new IDs to return. Defaults to 10.
- **sortby** (string, optional) - The key to sort the results by. Defaults to 'deltas'.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
- **file** (file-like object, optional) - The file to write to. Defaults to sys.stdout.
```

--------------------------------

### Highlight lines not covered by tests in Vim

Source: https://github.com/mgedmin/objgraph/blob/master/HACKING.rst

Use a Vim plugin to visually highlight lines of code that are not covered by the test suite while editing.

```vim
:HighlightCoverage
```

--------------------------------

### objgraph.is_proper_module

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Checks if an object is a proper module.

```APIDOC
## objgraph.is_proper_module

### Description
Checks if an object is a proper module.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **obj** (object) - Required - The object to check.
```

--------------------------------

### objgraph.most_common_types

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Returns the most common object types.

```APIDOC
## objgraph.most_common_types

### Description
Returns the most common object types.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **limit** (int, optional) - The maximum number of types to return. Defaults to 10.
- **objects** (iterable, optional) - An iterable of objects to consider. If not provided, all objects are considered.
- **shortnames** (bool, optional) - If True, use short type names. Defaults to True.
```

--------------------------------

### Define an Unpicklable Object

Source: https://github.com/mgedmin/objgraph/blob/master/docs/chain.txt

Defines a custom class that raises an error when its state is requested, simulating an unpicklable object.

```python
class MyUnpicklableObject(object):
    def __getstate__(self):
        raise NotImplementedError
```

--------------------------------

### Limitations of `objgraph.at()`

Source: https://github.com/mgedmin/objgraph/blob/master/docs/extra-info.md

The `objgraph.at()` function does not work for immutable types like strings, integers, or other simple types that are not tracked by the cyclic garbage collector. Attempting to use it with such types will result in no output.

```python
>>> a = 'a string'
>>> objgraph.at(id(a))
```

--------------------------------

### Find Leaking Objects

Source: https://github.com/mgedmin/objgraph/blob/master/docs/index.md

Use get_leaking_objects() to find objects that may have reference counting bugs. Be aware that this will include legitimate GC roots.

```python
>>> roots = objgraph.get_leaking_objects()
>>> len(roots)
4621
```

--------------------------------

### objgraph.count

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Counts the number of objects of a given type.

```APIDOC
## objgraph.count

### Description
Counts the number of objects of a given type.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **typename** (string) - Required - The name of the type to count.
- **objects** (iterable, optional) - An iterable of objects to consider. If not provided, all objects are considered.
```

--------------------------------

### Create a cyclic reference with an uncollectable object

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.md

This snippet demonstrates creating a cyclic reference involving an instance of `Nondestructible`. This cycle will cause the objects to be uncollectable by the garbage collector.

```python
x = Nondestructible()
y = []
z = []
x.append(y)
y.append(z)
z.append(x)
```

--------------------------------

### objgraph.find_ref_chain

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Finds a reference chain from an object to a predicate.

```APIDOC
## objgraph.find_ref_chain

### Description
Finds a reference chain from an object to a predicate.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **obj** (object) - Required - The starting object.
- **predicate** (callable) - Required - A callable that returns True if the target is found.
- **max_depth** (int, optional) - The maximum depth to search. Defaults to 20.
- **extra_ignore** (iterable, optional) - An iterable of objects to ignore during the search.
```

--------------------------------

### Collecting Uncollectable Garbage

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.txt

After removing external references to objects involved in a cycle, this code forces garbage collection and checks the `gc.garbage` list to confirm that one uncollectable object remains.

```python
import gc

del x, y, z
_ = gc.collect()
len(gc.garbage)
```

--------------------------------

### objgraph.find_backref_chain

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Finds a back-reference chain from an object to a predicate.

```APIDOC
## objgraph.find_backref_chain

### Description
Finds a back-reference chain from an object to a predicate.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **obj** (object) - Required - The starting object.
- **predicate** (callable) - Required - A callable that returns True if the target is found.
- **max_depth** (int, optional) - The maximum depth to search. Defaults to 20.
- **extra_ignore** (iterable, optional) - An iterable of objects to ignore during the search.
```

--------------------------------

### Define a class with a __del__ method

Source: https://github.com/mgedmin/objgraph/blob/master/docs/uncollectable.md

This snippet defines a class `Nondestructible` that inherits from `list` and includes a `__del__` method. This method prevents instances of this class from being garbage collected if they are part of a cycle.

```python
class Nondestructible(list):
    def __del__(self):
        pass
```

--------------------------------

### objgraph.get_leaking_objects

Source: https://github.com/mgedmin/objgraph/blob/master/docs/objgraph.txt

Finds objects that might be leaking memory.

```APIDOC
## objgraph.get_leaking_objects

### Description
Finds objects that might be leaking memory.

### Method
N/A (Python function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Parameters
- **objects** (iterable, optional) - An iterable of objects to consider. If not provided, all objects are considered.
```

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