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Calculated Shard: 1 (from laksa108)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa001.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://betterstack.com/community/questions/what-are-metaclasses-in-python/\')), getAhrefsUnparsedNoserviceFromURL(\'https://betterstack.com/community/questions/what-are-metaclasses-in-python/\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/betterstack.com\/community\/questions\/what-are-metaclasses-in-python\/","crawl_time":1775831682,"first_indexed_time":1674632367,"http_code":200,"src_unparsed":"com,betterstack!\/community\/questions\/what-are-metaclasses-in-python\/ s443","src_root_hash":"1143718778839325401","history_drop_reason":null,"meta_title":"What are metaclasses in Python? | Better Stack Community","meta_descriptions":["AI SRE and MCP server, incident management, on-call, logs, metrics, traces, and error tracking. 7,000+ happy customers. 60-day money back guarantee."],"attrs_boilerpipe_text":"Better Stack Team\nUpdated on January 24, 2023\nIn Python, a metaclass is the class of a class. It defines how a class behaves, including how it is created and how it manages its instances. A metaclass is defined by inheriting from the built-in\ntype\nclass, and it can define methods that customize the behavior of the class it creates. The class that a metaclass creates is called its \"metaclass instance\" or simply its \"instance.\" One use of metaclasses is to create singleton classes, classes with only one instance.\nHere's an example of a simple metaclass that creates a singleton class:\nCopied!\nHere, the\nSingleton\nmetaclass defines a\n__call__\nmethod that intercepts the creation of new instances of the class it creates. It keeps track of instances it has created in the\n_instances\ndictionary, and if an instance of the class already exists, it returns that instance instead of creating a new one. So, every time you create an instance of\nMySingletonClass\n, you get the same object.\nThis example is just a simple illustration of what metaclasses can do, and in most cases, this type of requirement could also be achieved by using other design patterns or python inbuilt modules like\nSingleton from module\nsingleton-decorator` .\nGot an article suggestion?\nLet us know\nExplore more\nThis work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.","attrs_markdown":"Platform\n\n[AI SRE Agentic root cause analysis](https:\/\/betterstack.com\/ai-sre)\n\n[Incident management & on-call Move fast when things break](https:\/\/betterstack.com\/incident-management)\n\n[Uptime monitoring The most reliable uptime monitoring](https:\/\/betterstack.com\/uptime)\n\n[Status page Communicate downtime & build trust](https:\/\/betterstack.com\/status-page)\n\n[Tracing eBPF-based OpenTelemetry-native tracing](https:\/\/betterstack.com\/tracing)\n\n[Log 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Stack](https:\/\/betterstack.com\/careers)\n\n[Engineering](https:\/\/betterstack.com\/careers\/engineering)\n\n[Security](https:\/\/betterstack.com\/security)\n\n[Blog](https:\/\/betterstack.com\/community\/blog)\n\n[Changelog](https:\/\/betterstack.com\/tag\/changelog)\n\n[Enterprise](https:\/\/betterstack.com\/enterprise)\n\n[Sign in](https:\/\/betterstack.com\/users\/sign-in) [Sign up](https:\/\/betterstack.com\/users\/sign-up)\n\nPlatform\n\n[Documentation](https:\/\/betterstack.com\/docs\/) [Pricing](https:\/\/betterstack.com\/pricing)\n\nCommunity\n\nCompany\n\n[Enterprise](https:\/\/betterstack.com\/enterprise)\n\nBack\n\n[AI SRE Agentic root cause analysis](https:\/\/betterstack.com\/ai-sre)\n\n[Incident management & on-call Move fast when things break](https:\/\/betterstack.com\/incident-management)\n\n[Uptime monitoring The most reliable uptime monitoring](https:\/\/betterstack.com\/uptime)\n\n[Status page Communicate downtime & build trust](https:\/\/betterstack.com\/status-page)\n\n[Tracing eBPF-based OpenTelemetry-native tracing](https:\/\/betterstack.com\/tracing)\n\n[Log management Collect insights across your stack](https:\/\/betterstack.com\/log-management)\n\n[Infrastructure monitoring OpenTelemetry-native infrastructure monitoring](https:\/\/betterstack.com\/infrastructure-monitoring)\n\n[Real user monitoring Session replay, web vitals & product analytics](https:\/\/betterstack.com\/real-user-monitoring)\n\n[Error tracking AI‑native error tracking built on Better Stack](https:\/\/betterstack.com\/error-tracking)\n\n[Data warehouse Time series data warehouse as an API](https:\/\/betterstack.com\/warehouse)\n\nBack\n\n[Community home](https:\/\/betterstack.com\/community)\n\n[Guides](https:\/\/betterstack.com\/community\/guides)\n\n[Questions](https:\/\/betterstack.com\/community\/questions)\n\n[Comparisons](https:\/\/betterstack.com\/community\/comparisons)\n\nBack\n\n[Work at Better Stack](https:\/\/betterstack.com\/careers)\n\n[Engineering](https:\/\/betterstack.com\/careers\/engineering)\n\n[Security](https:\/\/betterstack.com\/security)\n\n[Blog](https:\/\/betterstack.com\/community\/blog)\n\n[Changelog](https:\/\/betterstack.com\/tag\/changelog)\n\nQuestions\n\n[Community](https:\/\/betterstack.com\/community\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)   [Guides](https:\/\/betterstack.com\/community\/guides\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)   [Questions](https:\/\/betterstack.com\/community\/questions\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)   [Comparisons](https:\/\/betterstack.com\/community\/comparisons\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)   [Blog](https:\/\/betterstack.com\/community\/blog\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)\n\n- [Community](https:\/\/betterstack.com\/community\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)\n- [Guides](https:\/\/betterstack.com\/community\/guides\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)\n- [Questions](https:\/\/betterstack.com\/community\/questions\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)\n- [Comparisons](https:\/\/betterstack.com\/community\/comparisons\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)\n- [Blog](https:\/\/betterstack.com\/community\/blog\/?utm_content&utm_medium=questions&utm_source=community&utm_term=what-are-metaclasses-in-python)\n\n[Docs](https:\/\/betterstack.com\/docs\/) [Documentation](https:\/\/betterstack.com\/docs\/)\n\n# What are metaclasses in Python?\nBetter Stack Team\n\nUpdated on January 24, 2023\n\nIn Python, a metaclass is the class of a class. It defines how a class behaves, including how it is created and how it manages its instances. A metaclass is defined by inheriting from the built-in `type` class, and it can define methods that customize the behavior of the class it creates. The class that a metaclass creates is called its \"metaclass instance\" or simply its \"instance.\" One use of metaclasses is to create singleton classes, classes with only one instance.\n\nHere's an example of a simple metaclass that creates a singleton class:\n\nCopied\\!\n```\nclass Singleton(type):\n    _instances = {}\n    def __call__(cls, *args, **kwargs):\n        if cls not in cls._instances:\n            cls._instances[cls] = super().__call__(*args, **kwargs)\n        return cls._instances[cls]\n\nclass MySingletonClass(metaclass=Singleton):\n    pass\n\na = MySingletonClass()\nb = MySingletonClass()\nprint(a is b)  # True\n```\n\nHere, the `Singleton` metaclass defines a `__call__` method that intercepts the creation of new instances of the class it creates. It keeps track of instances it has created in the `_instances` dictionary, and if an instance of the class already exists, it returns that instance instead of creating a new one. So, every time you create an instance of `MySingletonClass`, you get the same object.\n\nThis example is just a simple illustration of what metaclasses can do, and in most cases, this type of requirement could also be achieved by using other design patterns or python inbuilt modules like `Singleton from module` singleton-decorator\\` .\n\nGot an article suggestion? [Let us know](mailto:hello@betterstack.com?subject=Suggestion%20for%20What%20are%20metaclasses%20in%20Python%3F&body=)\n\nExplore more\n\n[How to use the ternary conditional operator in Python? ![]() Questions](https:\/\/betterstack.com\/community\/questions\/how-to-use-ternary-operator-in-python\/)\n\n[What Does the “yield” Keyword Do in Python? ![]() Questions](https:\/\/betterstack.com\/community\/questions\/what-does-yield-keyword-do-python\/)\n\n[What Does if name == “main”: Do in Python? ![]() Questions](https:\/\/betterstack.com\/community\/questions\/what-does-if-name-is-main-do-in-python\/)\n\n[![Licensed under CC-BY-NC-SA]()](https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/)\n\nThis work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.\n\n- [How to use the ternary conditional operator in Python? The ternary conditional operator is a shortcut when writing simple conditional statements. If the condition is short and both true and false branches are short too, there is no need to use a multi-... ![]() Questions](https:\/\/betterstack.com\/community\/questions\/how-to-use-ternary-operator-in-python\/)\n- [What Does the “yield” Keyword Do in Python? To better understand what yield does, you need first to understand what generator and iterable are. What is iterable When you use a list or list-like structure, you can read the values from the lis... ![]() Questions](https:\/\/betterstack.com\/community\/questions\/what-does-yield-keyword-do-python\/)\n- [What Does if name == “main”: Do in Python? The if \\_\\_name\\_\\_ == \"main\" is a guarding block that is used to contain the code that should only run went the file in which this block is defined is run as a script. 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Exceptional customer support.\n\n[\\+1 (628) 900-3830](<tel:+1 (628) 900-3830>) [hello@betterstack.com](mailto:hello@betterstack.com)\n\n[Terms of Use](https:\/\/betterstack.com\/terms) [Privacy Policy](https:\/\/betterstack.com\/privacy) [GDPR](https:\/\/betterstack.com\/dpa)\n\n[System status](https:\/\/status.betterstack.com\/)\n\n© 2026 Better Stack, Inc.\n\n### Please accept cookies\nWe use cookies to authenticate users, improve the product user experience, and for [personalized ads](https:\/\/business.safety.google\/privacy\/). [Learn more.](https:\/\/betterstack.com\/privacy)\n\nDeny\n\nAccept required\n\nAccept all","attrs_readable_markdown":"Better Stack Team\n\nUpdated on January 24, 2023\n\nIn Python, a metaclass is the class of a class. It defines how a class behaves, including how it is created and how it manages its instances. A metaclass is defined by inheriting from the built-in `type` class, and it can define methods that customize the behavior of the class it creates. The class that a metaclass creates is called its \"metaclass instance\" or simply its \"instance.\" One use of metaclasses is to create singleton classes, classes with only one instance.\n\nHere's an example of a simple metaclass that creates a singleton class:\n\nCopied\\!\n\nHere, the `Singleton` metaclass defines a `__call__` method that intercepts the creation of new instances of the class it creates. It keeps track of instances it has created in the `_instances` dictionary, and if an instance of the class already exists, it returns that instance instead of creating a new one. So, every time you create an instance of `MySingletonClass`, you get the same object.\n\nThis example is just a simple illustration of what metaclasses can do, and in most cases, this type of requirement could also be achieved by using other design patterns or python inbuilt modules like `Singleton from module` singleton-decorator\\` .\n\nGot an article suggestion? [Let us know](mailto:hello@betterstack.com?subject=Suggestion%20for%20What%20are%20metaclasses%20in%20Python%3F&body=)\n\nExplore more\n\n[![Licensed under CC-BY-NC-SA](https:\/\/betterstack.com\/assets\/articles\/cc-by-nc-sa-198c1f75.png)](https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/)\n\nThis work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.","meta_canonical":null}

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5. Seen Status Check

ℹ️ Skipped - page is already crawled

📄

INDEXABLE

✅

CRAWLED

1 day ago

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ROBOTS ALLOWED

Page Info Filters

Filter	Status	Condition	Details
HTTP status	PASS	`download_http_code = 200`	HTTP 200
Age cutoff	PASS	`download_stamp > now() - 6 MONTH`	0 months ago
History drop	PASS	`isNull(history_drop_reason)`	No drop reason
Spam/ban	PASS	`fh_dont_index != 1 AND ml_spam_score = 0`	ml_spam_score=0
Canonical	PASS	`meta_canonical IS NULL OR = '' OR = src_unparsed`	Not set

Page Details

Property	Value
URL	https://betterstack.com/community/questions/what-are-metaclasses-in-python/
Last Crawled	2026-04-10 14:34:42 (1 day ago)
First Indexed	2023-01-25 07:39:27 (3 years ago)
HTTP Status Code	200
Meta Title	What are metaclasses in Python? \| Better Stack Community
Meta Description	AI SRE and MCP server, incident management, on-call, logs, metrics, traces, and error tracking. 7,000+ happy customers. 60-day money back guarantee.
Meta Canonical	null
Boilerpipe Text	Better Stack Team Updated on January 24, 2023 In Python, a metaclass is the class of a class. It defines how a class behaves, including how it is created and how it manages its instances. A metaclass is defined by inheriting from the built-in type class, and it can define methods that customize the behavior of the class it creates. The class that a metaclass creates is called its "metaclass instance" or simply its "instance." One use of metaclasses is to create singleton classes, classes with only one instance. Here's an example of a simple metaclass that creates a singleton class: Copied! Here, the Singleton metaclass defines a __call__ method that intercepts the creation of new instances of the class it creates. It keeps track of instances it has created in the _instances dictionary, and if an instance of the class already exists, it returns that instance instead of creating a new one. So, every time you create an instance of MySingletonClass , you get the same object. This example is just a simple illustration of what metaclasses can do, and in most cases, this type of requirement could also be achieved by using other design patterns or python inbuilt modules like Singleton from module singleton-decorator` . Got an article suggestion? Let us know Explore more This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
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Better Stack Team Updated on January 24, 2023 In Python, a metaclass is the class of a class. It defines how a class behaves, including how it is created and how it manages its instances. A metaclass is defined by inheriting from the built-in `type` class, and it can define methods that customize the behavior of the class it creates. The class that a metaclass creates is called its "metaclass instance" or simply its "instance." One use of metaclasses is to create singleton classes, classes with only one instance. Here's an example of a simple metaclass that creates a singleton class: Copied\! ``` class Singleton(type): _instances = {} def __call__(cls, args, kwargs): if cls not in cls._instances: cls._instances[cls] = super().__call__(args, **kwargs) return cls._instances[cls] class MySingletonClass(metaclass=Singleton): pass a = MySingletonClass() b = MySingletonClass() print(a is b) # True ``` Here, the `Singleton` metaclass defines a `__call__` method that intercepts the creation of new instances of the class it creates. It keeps track of instances it has created in the `_instances` dictionary, and if an instance of the class already exists, it returns that instance instead of creating a new one. So, every time you create an instance of `MySingletonClass`, you get the same object. This example is just a simple illustration of what metaclasses can do, and in most cases, this type of requirement could also be achieved by using other design patterns or python inbuilt modules like `Singleton from module` singleton-decorator\` . Got an article suggestion? 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Readable Markdown	Better Stack Team Updated on January 24, 2023 In Python, a metaclass is the class of a class. It defines how a class behaves, including how it is created and how it manages its instances. A metaclass is defined by inheriting from the built-in `type` class, and it can define methods that customize the behavior of the class it creates. The class that a metaclass creates is called its "metaclass instance" or simply its "instance." One use of metaclasses is to create singleton classes, classes with only one instance. Here's an example of a simple metaclass that creates a singleton class: Copied\! Here, the `Singleton` metaclass defines a `__call__` method that intercepts the creation of new instances of the class it creates. It keeps track of instances it has created in the `_instances` dictionary, and if an instance of the class already exists, it returns that instance instead of creating a new one. So, every time you create an instance of `MySingletonClass`, you get the same object. This example is just a simple illustration of what metaclasses can do, and in most cases, this type of requirement could also be achieved by using other design patterns or python inbuilt modules like `Singleton from module` singleton-decorator\` . Got an article suggestion? [Let us know](mailto:hello@betterstack.com?subject=Suggestion%20for%20What%20are%20metaclasses%20in%20Python%3F&body=) Explore more [![Licensed under CC-BY-NC-SA](https://betterstack.com/assets/articles/cc-by-nc-sa-198c1f75.png)](https://creativecommons.org/licenses/by-nc-sa/4.0/) This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
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