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Use f-strings (#4307)
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ammarnajjar committed Aug 23, 2020
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2 changes: 1 addition & 1 deletion docs/conf.py
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Expand Up @@ -49,7 +49,7 @@

# General information about the project.
project = 'Scrapy'
copyright = '2008–{}, Scrapy developers'.format(datetime.now().year)
copyright = f'2008–{datetime.now().year}, Scrapy developers'

# The version info for the project you're documenting, acts as replacement for
# |version| and |release|, also used in various other places throughout the
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6 changes: 3 additions & 3 deletions docs/intro/tutorial.rst
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Expand Up @@ -101,10 +101,10 @@ This is the code for our first Spider. Save it in a file named

def parse(self, response):
page = response.url.split("/")[-2]
filename = 'quotes-%s.html' % page
filename = f'quotes-{page}.html'
with open(filename, 'wb') as f:
f.write(response.body)
self.log('Saved file %s' % filename)
self.log(f'Saved file {filename}')


As you can see, our Spider subclasses :class:`scrapy.Spider <scrapy.spiders.Spider>`
Expand Down Expand Up @@ -190,7 +190,7 @@ for your spider::

def parse(self, response):
page = response.url.split("/")[-2]
filename = 'quotes-%s.html' % page
filename = f'quotes-{page}.html'
with open(filename, 'wb') as f:
f.write(response.body)

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138 changes: 69 additions & 69 deletions docs/topics/developer-tools.rst
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Expand Up @@ -5,9 +5,9 @@ Using your browser's Developer Tools for scraping
=================================================

Here is a general guide on how to use your browser's Developer Tools
to ease the scraping process. Today almost all browsers come with
to ease the scraping process. Today almost all browsers come with
built in `Developer Tools`_ and although we will use Firefox in this
guide, the concepts are applicable to any other browser.
guide, the concepts are applicable to any other browser.

In this guide we'll introduce the basic tools to use from a browser's
Developer Tools by scraping `quotes.toscrape.com`_.
Expand Down Expand Up @@ -41,16 +41,16 @@ Therefore, you should keep in mind the following things:
Inspecting a website
====================

By far the most handy feature of the Developer Tools is the `Inspector`
feature, which allows you to inspect the underlying HTML code of
any webpage. To demonstrate the Inspector, let's look at the
By far the most handy feature of the Developer Tools is the `Inspector`
feature, which allows you to inspect the underlying HTML code of
any webpage. To demonstrate the Inspector, let's look at the
`quotes.toscrape.com`_-site.

On the site we have a total of ten quotes from various authors with specific
tags, as well as the Top Ten Tags. Let's say we want to extract all the quotes
on this page, without any meta-information about authors, tags, etc.
tags, as well as the Top Ten Tags. Let's say we want to extract all the quotes
on this page, without any meta-information about authors, tags, etc.

Instead of viewing the whole source code for the page, we can simply right click
Instead of viewing the whole source code for the page, we can simply right click
on a quote and select ``Inspect Element (Q)``, which opens up the `Inspector`.
In it you should see something like this:

Expand Down Expand Up @@ -97,16 +97,16 @@ Then, back to your web browser, right-click on the ``span`` tag, select
>>> response.xpath('/html/body/div/div[2]/div[1]/div[1]/span[1]/text()').getall()
['“The world as we have created it is a process of our thinking. It cannot be changed without changing our thinking.”']

Adding ``text()`` at the end we are able to extract the first quote with this
Adding ``text()`` at the end we are able to extract the first quote with this
basic selector. But this XPath is not really that clever. All it does is
go down a desired path in the source code starting from ``html``. So let's
see if we can refine our XPath a bit:
go down a desired path in the source code starting from ``html``. So let's
see if we can refine our XPath a bit:

If we check the `Inspector` again we'll see that directly beneath our
expanded ``div`` tag we have nine identical ``div`` tags, each with the
same attributes as our first. If we expand any of them, we'll see the same
If we check the `Inspector` again we'll see that directly beneath our
expanded ``div`` tag we have nine identical ``div`` tags, each with the
same attributes as our first. If we expand any of them, we'll see the same
structure as with our first quote: Two ``span`` tags and one ``div`` tag. We can
expand each ``span`` tag with the ``class="text"`` inside our ``div`` tags and
expand each ``span`` tag with the ``class="text"`` inside our ``div`` tags and
see each quote:

.. code-block:: html
Expand All @@ -121,7 +121,7 @@ see each quote:


With this knowledge we can refine our XPath: Instead of a path to follow,
we'll simply select all ``span`` tags with the ``class="text"`` by using
we'll simply select all ``span`` tags with the ``class="text"`` by using
the `has-class-extension`_:

>>> response.xpath('//span[has-class("text")]/text()').getall()
Expand All @@ -130,45 +130,45 @@ the `has-class-extension`_:
'“There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle.”',
...]

And with one simple, cleverer XPath we are able to extract all quotes from
the page. We could have constructed a loop over our first XPath to increase
the number of the last ``div``, but this would have been unnecessarily
And with one simple, cleverer XPath we are able to extract all quotes from
the page. We could have constructed a loop over our first XPath to increase
the number of the last ``div``, but this would have been unnecessarily
complex and by simply constructing an XPath with ``has-class("text")``
we were able to extract all quotes in one line.
we were able to extract all quotes in one line.

The `Inspector` has a lot of other helpful features, such as searching in the
The `Inspector` has a lot of other helpful features, such as searching in the
source code or directly scrolling to an element you selected. Let's demonstrate
a use case:
a use case:

Say you want to find the ``Next`` button on the page. Type ``Next`` into the
search bar on the top right of the `Inspector`. You should get two results.
The first is a ``li`` tag with the ``class="next"``, the second the text
Say you want to find the ``Next`` button on the page. Type ``Next`` into the
search bar on the top right of the `Inspector`. You should get two results.
The first is a ``li`` tag with the ``class="next"``, the second the text
of an ``a`` tag. Right click on the ``a`` tag and select ``Scroll into View``.
If you hover over the tag, you'll see the button highlighted. From here
we could easily create a :ref:`Link Extractor <topics-link-extractors>` to
follow the pagination. On a simple site such as this, there may not be
we could easily create a :ref:`Link Extractor <topics-link-extractors>` to
follow the pagination. On a simple site such as this, there may not be
the need to find an element visually but the ``Scroll into View`` function
can be quite useful on complex sites.
can be quite useful on complex sites.

Note that the search bar can also be used to search for and test CSS
selectors. For example, you could search for ``span.text`` to find
all quote texts. Instead of a full text search, this searches for
exactly the ``span`` tag with the ``class="text"`` in the page.
selectors. For example, you could search for ``span.text`` to find
all quote texts. Instead of a full text search, this searches for
exactly the ``span`` tag with the ``class="text"`` in the page.

.. _topics-network-tool:

The Network-tool
================
While scraping you may come across dynamic webpages where some parts
of the page are loaded dynamically through multiple requests. While
this can be quite tricky, the `Network`-tool in the Developer Tools
of the page are loaded dynamically through multiple requests. While
this can be quite tricky, the `Network`-tool in the Developer Tools
greatly facilitates this task. To demonstrate the Network-tool, let's
take a look at the page `quotes.toscrape.com/scroll`_.
take a look at the page `quotes.toscrape.com/scroll`_.

The page is quite similar to the basic `quotes.toscrape.com`_-page,
but instead of the above-mentioned ``Next`` button, the page
automatically loads new quotes when you scroll to the bottom. We
could go ahead and try out different XPaths directly, but instead
The page is quite similar to the basic `quotes.toscrape.com`_-page,
but instead of the above-mentioned ``Next`` button, the page
automatically loads new quotes when you scroll to the bottom. We
could go ahead and try out different XPaths directly, but instead
we'll check another quite useful command from the Scrapy shell:

.. skip: next
Expand All @@ -179,31 +179,31 @@ we'll check another quite useful command from the Scrapy shell:
(...)
>>> view(response)
A browser window should open with the webpage but with one
crucial difference: Instead of the quotes we just see a greenish
bar with the word ``Loading...``.
A browser window should open with the webpage but with one
crucial difference: Instead of the quotes we just see a greenish
bar with the word ``Loading...``.

.. image:: _images/network_01.png
:width: 777
:height: 296
:alt: Response from quotes.toscrape.com/scroll

The ``view(response)`` command let's us view the response our
shell or later our spider receives from the server. Here we see
that some basic template is loaded which includes the title,
shell or later our spider receives from the server. Here we see
that some basic template is loaded which includes the title,
the login-button and the footer, but the quotes are missing. This
tells us that the quotes are being loaded from a different request
than ``quotes.toscrape/scroll``.
than ``quotes.toscrape/scroll``.

If you click on the ``Network`` tab, you will probably only see
two entries. The first thing we do is enable persistent logs by
clicking on ``Persist Logs``. If this option is disabled, the
If you click on the ``Network`` tab, you will probably only see
two entries. The first thing we do is enable persistent logs by
clicking on ``Persist Logs``. If this option is disabled, the
log is automatically cleared each time you navigate to a different
page. Enabling this option is a good default, since it gives us
control on when to clear the logs.
page. Enabling this option is a good default, since it gives us
control on when to clear the logs.

If we reload the page now, you'll see the log get populated with six
new requests.
new requests.

.. image:: _images/network_02.png
:width: 777
Expand All @@ -212,31 +212,31 @@ new requests.

Here we see every request that has been made when reloading the page
and can inspect each request and its response. So let's find out
where our quotes are coming from:
where our quotes are coming from:

First click on the request with the name ``scroll``. On the right
First click on the request with the name ``scroll``. On the right
you can now inspect the request. In ``Headers`` you'll find details
about the request headers, such as the URL, the method, the IP-address,
and so on. We'll ignore the other tabs and click directly on ``Response``.

What you should see in the ``Preview`` pane is the rendered HTML-code,
that is exactly what we saw when we called ``view(response)`` in the
shell. Accordingly the ``type`` of the request in the log is ``html``.
The other requests have types like ``css`` or ``js``, but what
interests us is the one request called ``quotes?page=1`` with the
type ``json``.
What you should see in the ``Preview`` pane is the rendered HTML-code,
that is exactly what we saw when we called ``view(response)`` in the
shell. Accordingly the ``type`` of the request in the log is ``html``.
The other requests have types like ``css`` or ``js``, but what
interests us is the one request called ``quotes?page=1`` with the
type ``json``.

If we click on this request, we see that the request URL is
If we click on this request, we see that the request URL is
``http://quotes.toscrape.com/api/quotes?page=1`` and the response
is a JSON-object that contains our quotes. We can also right-click
on the request and open ``Open in new tab`` to get a better overview.
on the request and open ``Open in new tab`` to get a better overview.

.. image:: _images/network_03.png
:width: 777
:height: 375
:alt: JSON-object returned from the quotes.toscrape API

With this response we can now easily parse the JSON-object and
With this response we can now easily parse the JSON-object and
also request each page to get every quote on the site::

import scrapy
Expand All @@ -255,17 +255,17 @@ also request each page to get every quote on the site::
yield {"quote": quote["text"]}
if data["has_next"]:
self.page += 1
url = "http://quotes.toscrape.com/api/quotes?page={}".format(self.page)
url = f"http://quotes.toscrape.com/api/quotes?page={self.page}"
yield scrapy.Request(url=url, callback=self.parse)

This spider starts at the first page of the quotes-API. With each
response, we parse the ``response.text`` and assign it to ``data``.
This lets us operate on the JSON-object like on a Python dictionary.
This spider starts at the first page of the quotes-API. With each
response, we parse the ``response.text`` and assign it to ``data``.
This lets us operate on the JSON-object like on a Python dictionary.
We iterate through the ``quotes`` and print out the ``quote["text"]``.
If the handy ``has_next`` element is ``true`` (try loading
If the handy ``has_next`` element is ``true`` (try loading
`quotes.toscrape.com/api/quotes?page=10`_ in your browser or a
page-number greater than 10), we increment the ``page`` attribute
and ``yield`` a new request, inserting the incremented page-number
page-number greater than 10), we increment the ``page`` attribute
and ``yield`` a new request, inserting the incremented page-number
into our ``url``.

.. _requests-from-curl:
Expand Down Expand Up @@ -298,7 +298,7 @@ Note that to translate a cURL command into a Scrapy request,
you may use `curl2scrapy <https://michael-shub.github.io/curl2scrapy/>`_.

As you can see, with a few inspections in the `Network`-tool we
were able to easily replicate the dynamic requests of the scrolling
were able to easily replicate the dynamic requests of the scrolling
functionality of the page. Crawling dynamic pages can be quite
daunting and pages can be very complex, but it (mostly) boils down
to identifying the correct request and replicating it in your spider.
Expand Down
6 changes: 3 additions & 3 deletions docs/topics/exporters.rst
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Expand Up @@ -57,7 +57,7 @@ value of one of their fields::
adapter = ItemAdapter(item)
year = adapter['year']
if year not in self.year_to_exporter:
f = open('{}.xml'.format(year), 'wb')
f = open(f'{year}.xml', 'wb')
exporter = XmlItemExporter(f)
exporter.start_exporting()
self.year_to_exporter[year] = exporter
Expand Down Expand Up @@ -98,7 +98,7 @@ Example::
import scrapy

def serialize_price(value):
return '$ %s' % str(value)
return f'$ {str(value)}'

class Product(scrapy.Item):
name = scrapy.Field()
Expand All @@ -122,7 +122,7 @@ Example::

def serialize_field(self, field, name, value):
if field == 'price':
return '$ %s' % str(value)
return f'$ {str(value)}'
return super(Product, self).serialize_field(field, name, value)

.. _topics-exporters-reference:
Expand Down
6 changes: 3 additions & 3 deletions docs/topics/item-pipeline.rst
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Expand Up @@ -96,7 +96,7 @@ contain a price::
adapter['price'] = adapter['price'] * self.vat_factor
return item
else:
raise DropItem("Missing price in %s" % item)
raise DropItem(f"Missing price in {item}")


Write items to a JSON file
Expand Down Expand Up @@ -211,7 +211,7 @@ item.
# Save screenshot to file, filename will be hash of url.
url = adapter["url"]
url_hash = hashlib.md5(url.encode("utf8")).hexdigest()
filename = "{}.png".format(url_hash)
filename = f"{url_hash}.png"
with open(filename, "wb") as f:
f.write(response.body)

Expand Down Expand Up @@ -240,7 +240,7 @@ returns multiples items with the same id::
def process_item(self, item, spider):
adapter = ItemAdapter(item)
if adapter['id'] in self.ids_seen:
raise DropItem("Duplicate item found: %r" % item)
raise DropItem(f"Duplicate item found: {item!r}")
else:
self.ids_seen.add(adapter['id'])
return item
Expand Down
2 changes: 1 addition & 1 deletion docs/topics/leaks.rst
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Expand Up @@ -102,7 +102,7 @@ A real example
Let's see a concrete example of a hypothetical case of memory leaks.
Suppose we have some spider with a line similar to this one::

return Request("http://www.somenastyspider.com/product.php?pid=%d" % product_id,
return Request(f"http://www.somenastyspider.com/product.php?pid={product_id}",
callback=self.parse, cb_kwargs={'referer': response})

That line is passing a response reference inside a request which effectively
Expand Down
7 changes: 4 additions & 3 deletions docs/topics/selectors.rst
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Expand Up @@ -328,8 +328,9 @@ too. Here's an example:
'<a href="image5.html">Name: My image 5 <br><img src="image5_thumb.jpg"></a>']

>>> for index, link in enumerate(links):
... args = (index, link.xpath('@href').get(), link.xpath('img/@src').get())
... print('Link number %d points to url %r and image %r' % args)
... href_xpath = link.xpath('@href').get()
... img_xpath = link.xpath('img/@src').get()
... print(f'Link number {index} points to url {href_xpath!r} and image {img_xpath!r}')
Link number 0 points to url 'image1.html' and image 'image1_thumb.jpg'
Link number 1 points to url 'image2.html' and image 'image2_thumb.jpg'
Link number 2 points to url 'image3.html' and image 'image3_thumb.jpg'
Expand Down Expand Up @@ -822,7 +823,7 @@ with groups of itemscopes and corresponding itemprops::
... props = scope.xpath('''
... set:difference(./descendant::*/@itemprop,
... .//*[@itemscope]/*/@itemprop)''')
... print(" properties: %s" % (props.getall()))
... print(f" properties: {props.getall()}")
... print("")

current scope: ['http://schema.org/Product']
Expand Down
2 changes: 1 addition & 1 deletion docs/topics/settings.rst
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Expand Up @@ -110,7 +110,7 @@ In a spider, the settings are available through ``self.settings``::
start_urls = ['http://example.com']

def parse(self, response):
print("Existing settings: %s" % self.settings.attributes.keys())
print(f"Existing settings: {self.settings.attributes.keys()}")

.. note::
The ``settings`` attribute is set in the base Spider class after the spider
Expand Down
4 changes: 2 additions & 2 deletions docs/topics/spiders.rst
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Expand Up @@ -279,7 +279,7 @@ Spiders can access arguments in their `__init__` methods::

def __init__(self, category=None, *args, **kwargs):
super(MySpider, self).__init__(*args, **kwargs)
self.start_urls = ['http://www.example.com/categories/%s' % category]
self.start_urls = [f'http://www.example.com/categories/{category}']
# ...

The default `__init__` method will take any spider arguments
Expand All @@ -292,7 +292,7 @@ The above example can also be written as follows::
name = 'myspider'

def start_requests(self):
yield scrapy.Request('http://www.example.com/categories/%s' % self.category)
yield scrapy.Request(f'http://www.example.com/categories/{self.category}')

Keep in mind that spider arguments are only strings.
The spider will not do any parsing on its own.
Expand Down

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