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# Settings

The Scrapy settings allows you to customize the behaviour of all Scrapy components, including the core, extensions, pipelines and spiders themselves.

The infrastructure of the settings provides a global namespace of key-value mappings that the code can use to pull configuration values from. The settings can be populated through different mechanisms, which are described below.

The settings are also the mechanism for selecting the currently active Scrapy project (in case you have many).

For a list of available built-in settings see: Built-in settings reference.

## Designating the settings

When you use Scrapy, you have to tell it which settings you’re using. You can do this by using an environment variable, `SCRAPY_SETTINGS_MODULE`.

The value of `SCRAPY_SETTINGS_MODULE` should be in Python path syntax, e.g. `myproject.settings`. Note that the settings module should be on the Python import search path.

## Populating the settings

Settings can be populated using different mechanisms, each of which having a different precedence. Here is the list of them in decreasing order of precedence:

> 1. Global overrides (most precedence)
> 2. Project settings module
> 3. Default settings per-command
> 4. Default global settings (less precedence)

These mechanisms are described in more detail below.

### 1. Global overrides

Global overrides are the ones that take most precedence, and are usually populated by command-line options.

Example::

      >>> from scrapy.conf import settings
      >>> settings.overrides['LOG_ENABLED'] = True

You can also override one (or more) settings from command line using the `-s` (or `--set`) command line option.

Example:

    scrapy crawl domain.com -s LOG_FILE=scrapy.log

### 2. Project settings module

The project settings module is the standard configuration file for your Scrapy project. It’s where most of your custom settings will be populated. For example:: `myproject.settings`.

### 3. Default settings per-command

Each Scrapy tool command can have its own default settings, which override the global default settings. Those custom command settings are specified in the `default_settings` attribute of the command class.

### 4. Default global settings

The global defaults are located in the `scrapy.settings.default_settings` module and documented in the Built-in settings reference section.

## How to access settings

Here’s an example of the simplest way to access settings from Python code:

    >>> from scrapy.conf import settings
    >>> print settings['LOG_ENABLED']
    True

In other words, settings can be accesed like a dict, but it’s usually preferred to extract the setting in the format you need it to avoid type errors. In order to do that you’ll have to use one of the following methods:

class `scrapy.conf.``Settings`

  There is a (singleton) Settings object automatically instantiated when the `scrapy.conf` module is loaded, and it’s usually accessed like this:

      >>> from scrapy.conf import settings

  > `get`(name, default=None)

  >   Get a setting value without affecting its original type.

  >   Parameters:

  >   - name (string) – the setting name
  >   - default (any) – the value to return if no setting is found

  > `getbool`(name, default=False)

  >   Get a setting value as a boolean. For example, both `1` and `'1'`, and `True` return `True`, while `0`, `'0'`, `False` and `None` return `False```

  >   For example, settings populated through environment variables set to `'0'` will return `False` when using this method.

  >   Parameters:

  >   - name (string) – the setting name
  >   - default (any) – the value to return if no setting is found

  > `getint`(name, default=0)

  >   Get a setting value as an int

  >   Parameters:

  >   - name (string) – the setting name
  >   - default (any) – the value to return if no setting is found

  > `getfloat`(name, default=0.0)

  >   Get a setting value as a float

  >   Parameters:

  >   - name (string) – the setting name
  >   - default (any) – the value to return if no setting is found

  > `getlist`(name, default=None)

  >   Get a setting value as a list. If the setting original type is a list it will be returned verbatim. If it’s a string it will be split by ”,”.

  >   For example, settings populated through environment variables set to `'one,two'` will return a list [‘one’, ‘two’] when using this method.

  >   Parameters:

  >   - name (string) – the setting name
  >   - default (any) – the value to return if no setting is found

## Rationale for setting names

Setting names are usually prefixed with the component that they configure. For example, proper setting names for a fictional robots.txt extension would be `ROBOTSTXT_ENABLED`, `ROBOTSTXT_OBEY`, `ROBOTSTXT_CACHEDIR`, etc.

## Built-in settings reference

Here’s a list of all available Scrapy settings, in alphabetical order, along with their default values and the scope where they apply.

The scope, where available, shows where the setting is being used, if it’s tied to any particular component. In that case the module of that component will be shown, typically an extension, middleware or pipeline. It also means that the component must be enabled in order for the setting to have any effect.

### AWS_ACCESS_KEY_ID

Default: `None`

The AWS access key used by code that requires access to Amazon Web services, such as the S3 feed storage backend.

### AWS_SECRET_ACCESS_KEY

Default: `None`

The AWS secret key used by code that requires access to Amazon Web services, such as the S3 feed storage backend.

### BOT_NAME

Default: `'scrapybot'`

The name of the bot implemented by this Scrapy project (also known as the project name). This will be used to construct the User-Agent by default, and also for logging.

It’s automatically populated with your project name when you create your project with the `startproject` command.

### BOT_VERSION

Default: `1.0`

The version of the bot implemented by this Scrapy project. This will be used to construct the User-Agent by default.

### CONCURRENT_ITEMS

Default: `100`

Maximum number of concurrent items (per response) to process in parallel in the Item Processor (also known as the Item Pipeline).

### CONCURRENT_REQUESTS

Default: `16`

The maximum number of concurrent (ie. simultaneous) requests that will be performed by the Scrapy downloader.

### CONCURRENT_REQUESTS_PER_DOMAIN

Default: `8`

The maximum number of concurrent (ie. simultaneous) requests that will be performed to any single domain.

### CONCURRENT_REQUESTS_PER_IP

Default: `0`

The maximum number of concurrent (ie. simultaneous) requests that will be performed to any single IP. If non-zero, the `CONCURRENT_REQUESTS_PER_DOMAIN` setting is ignored, and this one is used instead. In other words, concurrency limits will be applied per IP, not per domain.

### DEFAULT_ITEM_CLASS

Default: `'scrapy.item.Item'`

The default class that will be used for instantiating items in the the Scrapy shell.

### DEFAULT_REQUEST_HEADERS

Default:

    {
        'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
        'Accept-Language': 'en',
    }

The default headers used for Scrapy HTTP Requests. They’re populated in the `DefaultHeadersMiddleware`.

### DEFAULT_RESPONSE_ENCODING

Default: `'ascii'`

The default encoding to use for `TextResponse` objects (and subclasses) when no encoding is declared and no encoding could be inferred from the body.

### DEPTH_LIMIT

Default: `0`

The maximum depth that will be allowed to crawl for any site. If zero, no limit will be imposed.

### DEPTH_PRIORITY

Default: `0`

An integer that is used to adjust the request priority based on its depth.

If zero, no priority adjustment is made from depth.

### DEPTH_STATS

Default: `True`

Whether to collect maximum depth stats.

### DEPTH_STATS_VERBOSE

Default: `False`

Whether to collect verbose depth stats. If this is enabled, the number of requests for each depth is collected in the stats.

### DNSCACHE_ENABLED

Default: `True`

Whether to enable DNS in-memory cache.

### DOWNLOADER_DEBUG

Default: `False`

Whether to enable the Downloader debugging mode.

### DOWNLOADER_MIDDLEWARES

Default:: `{}`

A dict containing the downloader middlewares enabled in your project, and their orders. For more info see Activating a downloader middleware.

### DOWNLOADER_MIDDLEWARES_BASE

Default:

    {
        'scrapy.contrib.downloadermiddleware.robotstxt.RobotsTxtMiddleware': 100,
        'scrapy.contrib.downloadermiddleware.httpauth.HttpAuthMiddleware': 300,
        'scrapy.contrib.downloadermiddleware.downloadtimeout.DownloadTimeoutMiddleware': 350,
        'scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware': 400,
        'scrapy.contrib.downloadermiddleware.retry.RetryMiddleware': 500,
        'scrapy.contrib.downloadermiddleware.defaultheaders.DefaultHeadersMiddleware': 550,
        'scrapy.contrib.downloadermiddleware.redirect.RedirectMiddleware': 600,
        'scrapy.contrib.downloadermiddleware.cookies.CookiesMiddleware': 700,
        'scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware': 750,
        'scrapy.contrib.downloadermiddleware.httpcompression.HttpCompressionMiddleware': 800,
        'scrapy.contrib.downloadermiddleware.chunked.ChunkedTransferMiddleware': 830,
        'scrapy.contrib.downloadermiddleware.stats.DownloaderStats': 850,
        'scrapy.contrib.downloadermiddleware.httpcache.HttpCacheMiddleware': 900,
    }

A dict containing the downloader middlewares enabled by default in Scrapy. You should never modify this setting in your project, modify `DOWNLOADER_MIDDLEWARES` instead. For more info see Activating a downloader middleware.

### DOWNLOADER_STATS

Default: `True`

Whether to enable downloader stats collection.

### DOWNLOAD_DELAY

Default: `0`

The amount of time (in secs) that the downloader should wait before downloading consecutive pages from the same spider. This can be used to throttle the crawling speed to avoid hitting servers too hard. Decimal numbers are supported. Example:

    DOWNLOAD_DELAY = 0.25    # 250 ms of delay

This setting is also affected by the `RANDOMIZE_DOWNLOAD_DELAY` setting (which is enabled by default). By default, Scrapy doesn’t wait a fixed amount of time between requests, but uses a random interval between 0.5 and 1.5 * `DOWNLOAD_DELAY`.

You can also change this setting per spider.

### DOWNLOAD_HANDLERS

Default: `{}`

A dict containing the request downloader handlers enabled in your project. See DOWNLOAD_HANDLERS_BASE for example format.

### DOWNLOAD_HANDLERS_BASE

Default:

    {
        'file': 'scrapy.core.downloader.handlers.file.FileDownloadHandler',
        'http': 'scrapy.core.downloader.handlers.http.HttpDownloadHandler',
        'https': 'scrapy.core.downloader.handlers.http.HttpDownloadHandler',
        's3': 'scrapy.core.downloader.handlers.s3.S3DownloadHandler',
    }

A dict containing the request download handlers enabled by default in Scrapy. You should never modify this setting in your project, modify `DOWNLOAD_HANDLERS` instead.

### DOWNLOAD_TIMEOUT

Default: `180`

The amount of time (in secs) that the downloader will wait before timing out.

### DUPEFILTER_CLASS

Default: `'scrapy.dupefilter.RFPDupeFilter'`

The class used to detect and filter duplicate requests.

The default (`RFPDupeFilter`) filters based on request fingerprint using the `scrapy.utils.request.request_fingerprint` function.

### EDITOR

The editor to use for editing spiders with the `edit` command. It defaults to the `EDITOR` environment variable, if set. Otherwise, it defaults to `vi` (on Unix systems) or the IDLE editor (on Windows).

### ENCODING_ALIASES

Default: `{}`

A mapping of custom encoding aliases for your project, where the keys are the aliases (and must be lower case) and the values are the encodings they map to.

This setting extends the `ENCODING_ALIASES_BASE` setting which contains some default mappings.

### ENCODING_ALIASES_BASE

Default:

    {
        # gb2312 is superseded by gb18030
        'gb2312': 'gb18030',
        'chinese': 'gb18030',
        'csiso58gb231280': 'gb18030',
        'euc- cn': 'gb18030',
        'euccn': 'gb18030',
        'eucgb2312-cn': 'gb18030',
        'gb2312-1980': 'gb18030',
        'gb2312-80': 'gb18030',
        'iso- ir-58': 'gb18030',
        # gbk is superseded by gb18030
        'gbk': 'gb18030',
        '936': 'gb18030',
        'cp936': 'gb18030',
        'ms936': 'gb18030',
        # latin_1 is a subset of cp1252
        'latin_1': 'cp1252',
        'iso-8859-1': 'cp1252',
        'iso8859-1': 'cp1252',
        '8859': 'cp1252',
        'cp819': 'cp1252',
        'latin': 'cp1252',
        'latin1': 'cp1252',
        'l1': 'cp1252',
        # others
        'zh-cn': 'gb18030',
        'win-1251': 'cp1251',
        'macintosh' : 'mac_roman',
        'x-sjis': 'shift_jis',
    }

The default encoding aliases defined in Scrapy. Don’t override this setting in your project, override `ENCODING_ALIASES` instead.

The reason why ISO-8859-1 (and all its aliases) are mapped to CP1252 is due to a well known browser hack. For more information see: Character encodings in HTML.

### EXTENSIONS

Default:: `{}`

A dict containing the extensions enabled in your project, and their orders.

### EXTENSIONS_BASE

Default:

    {
        'scrapy.contrib.corestats.CoreStats': 0,
        'scrapy.webservice.WebService': 0,
        'scrapy.telnet.TelnetConsole': 0,
        'scrapy.contrib.memusage.MemoryUsage': 0,
        'scrapy.contrib.memdebug.MemoryDebugger': 0,
        'scrapy.contrib.closespider.CloseSpider': 0,
        'scrapy.contrib.feedexport.FeedExporter': 0,
        'scrapy.contrib.spidercontext.SpiderContext': 0,
        'scrapy.contrib.logstats.LogStats': 0,
        'scrapy.contrib.spiderstate.SpiderState': 0,
    }

The list of available extensions. Keep in mind that some of them need to be enabled through a setting. By default, this setting contains all stable built-in extensions.

For more information See the extensions user guide and the list of available extensions.

### ITEM_PIPELINES

Default: `[]`

The item pipelines to use (a list of classes).

Example:

    ITEM_PIPELINES = [
        'mybot.pipeline.validate.ValidateMyItem',
        'mybot.pipeline.validate.StoreMyItem'
    ]

### LOG_ENABLED

Default: `True`

Whether to enable logging.

### LOG_ENCODING

Default: `'utf-8'`

The encoding to use for logging.

### LOG_FILE

Default: `None`

File name to use for logging output. If None, standard error will be used.

### LOG_LEVEL

Default: `'DEBUG'`

Minimum level to log. Available levels are: CRITICAL, ERROR, WARNING, INFO, DEBUG. For more info see Logging.

### LOG_STDOUT

Default: `False`

If `True`, all standard output (and error) of your process will be redirected to the log. For example if you `print 'hello'` it will appear in the Scrapy log.

### MEMDEBUG_ENABLED

Default: `False`

Whether to enable memory debugging.

### MEMDEBUG_NOTIFY

Default: `[]`

When memory debugging is enabled a memory report will be sent to the specified addresses if this setting is not empty, otherwise the report will be written to the log.

Example:

    MEMDEBUG_NOTIFY = ['user@example.com']

### MEMUSAGE_ENABLED

Default: `False`

Scope: `scrapy.contrib.memusage`

Whether to enable the memory usage extension that will shutdown the Scrapy process when it exceeds a memory limit, and also notify by email when that happened.

See Memory usage extension.

### MEMUSAGE_LIMIT_MB

Default: `0`

Scope: `scrapy.contrib.memusage`

The maximum amount of memory to allow (in megabytes) before shutting down Scrapy (if MEMUSAGE_ENABLED is True). If zero, no check will be performed.

See Memory usage extension.

### MEMUSAGE_NOTIFY_MAIL

Default: `False`

Scope: `scrapy.contrib.memusage`

A list of emails to notify if the memory limit has been reached.

Example:

    MEMUSAGE_NOTIFY_MAIL = ['user@example.com']

See Memory usage extension.

### MEMUSAGE_REPORT

Default: `False`

Scope: `scrapy.contrib.memusage`

Whether to send a memory usage report after each spider has been closed.

See Memory usage extension.

### MEMUSAGE_WARNING_MB

Default: `0`

Scope: `scrapy.contrib.memusage`

The maximum amount of memory to allow (in megabytes) before sending a warning email notifying about it. If zero, no warning will be produced.

### NEWSPIDER_MODULE

Default: `''`

Module where to create new spiders using the `genspider` command.

Example:

    NEWSPIDER_MODULE = 'mybot.spiders_dev'

### RANDOMIZE_DOWNLOAD_DELAY

Default: `True`

If enabled, Scrapy will wait a random amount of time (between 0.5 and 1.5 * `DOWNLOAD_DELAY`) while fetching requests from the same spider.

This randomization decreases the chance of the crawler being detected (and subsequently blocked) by sites which analyze requests looking for statistically significant similarities in the time between their requests.

The randomization policy is the same used by wget `--random-wait` option.

If `DOWNLOAD_DELAY` is zero (default) this option has no effect.

### REDIRECT_MAX_TIMES

Default: `20`

Defines the maximun times a request can be redirected. After this maximun the request’s response is returned as is. We used Firefox default value for the same task.

### REDIRECT_MAX_METAREFRESH_DELAY

Default: `100`

Some sites use meta-refresh for redirecting to a session expired page, so we restrict automatic redirection to a maximum delay (in seconds)

### REDIRECT_PRIORITY_ADJUST

Default: `+2`

Adjust redirect request priority relative to original request. A negative priority adjust means more priority.

### ROBOTSTXT_OBEY

Default: `False`

Scope: `scrapy.contrib.downloadermiddleware.robotstxt`

If enabled, Scrapy will respect robots.txt policies. For more information see RobotsTxtMiddleware

### SCHEDULER

Default: `'scrapy.core.scheduler.Scheduler'`

The scheduler to use for crawling.

### SPIDER_MIDDLEWARES

Default:: `{}`

A dict containing the spider middlewares enabled in your project, and their orders. For more info see Activating a spider middleware.

### SPIDER_MIDDLEWARES_BASE

Default:

    {
        'scrapy.contrib.spidermiddleware.httperror.HttpErrorMiddleware': 50,
        'scrapy.contrib.spidermiddleware.offsite.OffsiteMiddleware': 500,
        'scrapy.contrib.spidermiddleware.referer.RefererMiddleware': 700,
        'scrapy.contrib.spidermiddleware.urllength.UrlLengthMiddleware': 800,
        'scrapy.contrib.spidermiddleware.depth.DepthMiddleware': 900,
    }

A dict containing the spider middlewares enabled by default in Scrapy. You should never modify this setting in your project, modify `SPIDER_MIDDLEWARES` instead. For more info see Activating a spider middleware.

### SPIDER_MODULES

Default: `[]`

A list of modules where Scrapy will look for spiders.

Example:

    SPIDER_MODULES = ['mybot.spiders_prod', 'mybot.spiders_dev']

### STATS_CLASS

Default: `'scrapy.statscol.MemoryStatsCollector'`

The class to use for collecting stats (must implement the Stats Collector API, or subclass the StatsCollector class).

### STATS_DUMP

Default: `True`

Dump (to the Scrapy log) the Scrapy stats collected during the crawl. The spider-specific stats are logged when the spider is closed, while the global stats are dumped when the Scrapy process finishes.

For more info see: Stats Collection.

### STATS_ENABLED

Default: `True`

Enable stats collection.

### STATSMAILER_RCPTS

Default: `[]` (empty list)

Send Scrapy stats after spiders finish scraping. See `StatsMailer` for more info.

### TELNETCONSOLE_ENABLED

Default: `True`

A boolean which specifies if the telnet console will be enabled (provided its extension is also enabled).

### TELNETCONSOLE_PORT

Default: `[6023, 6073]`

The port range to use for the telnet console. If set to `None` or `0`, a dynamically assigned port is used. For more info see Telnet Console.

### TEMPLATES_DIR

Default: `templates` dir inside scrapy module

The directory where to look for templates when creating new projects with `startproject` command.

### URLLENGTH_LIMIT

Default: `2083`

Scope: `contrib.spidermiddleware.urllength`

The maximum URL length to allow for crawled URLs. For more information about the default value for this setting see: http://www.boutell.com/newfaq/misc/urllength.html

### USER_AGENT

Default: `"%s/%s" % (BOT_NAME, BOT_VERSION)`

The default User-Agent to use when crawling, unless overridden.

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