Crawling and Scraping Analysis
After crawling a website, or a bunch of URLs, you mostly likely want to analyze the data and gain a better undersanding of the website's structure, strategy, and content. You probably also want to check for technical issues that the site might have.
This module provides a few ready-made functions to help in anayzing crawl data.
There are certain columns in the crawl DataFrame that can be analyzed separately and independently, like page size and status codes. They can of course be analyzed together with other columns like URL and title to put these columns and their data in context.
There are also groups of columns the can be thought of as describing one full aspect of a website, yet spread across a few columns. For exmaple:
Analyzing crawled images
Every crawled URL typically contains multiple images. Every image in turn has multiple attributes (src, alt, width, etc.) The number of images per URL is not the same, and not all images have the same attributes. So we need a way to unpack all these data points in a tidy (long form) DataFrame to get an idea of how images (and their attributes) are used and distributed across the crawled website (URLs).
Once you have read a crawl output file into a DataFrame, you can summarize the images in this DataFrame as follows:
>>> import advertools as adv
>>> import pandas as pd
>>> crawldf = pd.read_json('path/to/output_file.jl', lines=True)
>>> img_df = adv.crawlytics.images(crawldf)
>>> img_df
url |
img_src |
img_alt |
img_loading |
img_sizes |
img_decoding |
img_width |
img_height |
img_border |
|
|---|---|---|---|---|---|---|---|---|---|
0 |
/vi-assets/static-assets/icon-the-morning_144x144-b12a6923b6ad9102b766352261b1a847.webp |
The Morning Logo |
nan |
nan |
nan |
nan |
nan |
||
0 |
/vi-assets/static-assets/icon-the-upshot_144x144-0b1553ff703bbd07ac8fe73e6d215888.webp |
The Upshot Logo |
nan |
nan |
nan |
nan |
nan |
||
0 |
The Daily Logo |
nan |
nan |
nan |
nan |
nan |
|||
1 |
https://static.nytimes.com/email-images/NYT-Newsletters-Europe-Icon-500px.jpg |
morning briefing |
nan |
nan |
nan |
nan |
nan |
nan |
|
2 |
https://static.nytimes.com/email-images/NYT-Newsletters-AustraliaLetter-Icon-500px.jpg |
australia-letter |
nan |
nan |
nan |
nan |
nan |
nan |
|
3 |
https://static.nytimes.com/email-images/NYT-Newsletters-SONL-TheInterpreter-Icon-500px.jpg |
the interpreter |
nan |
nan |
nan |
nan |
nan |
nan |
|
4 |
nan |
(min-width: 1024px) 205px, 150px |
async |
150 |
100 |
nan |
|||
4 |
nan |
(min-width: 1024px) 205px, 150px |
async |
150 |
100 |
nan |
|||
4 |
nan |
(min-width: 1024px) 205px, 150px |
async |
150 |
100 |
nan |
As you can see, for every URL we have all available image attributes listed, and in many cases with those attributes empty, because they were not used for that particular image. Also note that each image is represented independently on its own row, and mapped to the URL on which it was found, which can be seen in the first column. This is why we have the same URL repeated, to represent data for each image. You can use those URLs to get more data about the URL of interest from the crawl DataFrame.
Let's get a quick overview of the usage of the various image attributes in this DataFrame. We do this by checking whether a tag is notna and get the averages.
>>> img_df.notna().mean().sort_values(ascending=False).to_frame().round(2)
url |
1 |
img_src |
0.99 |
img_alt |
0.99 |
img_width |
0.86 |
img_height |
0.86 |
img_srcset |
0.25 |
img_sizes |
0.25 |
img_decoding |
0.25 |
img_loading |
0.01 |
img_border |
0 |
We can now see that almost all (99%) of our images have src and alt attributes. About 86% have width and height, and so on. This immediately gives us an overview of how our images are managed on the site. We can easily estimate the size of the issues if any, and plan our work accordingly.
Analyzing links in a crawled website
Another important aspect of any webpage/website is understanding how its pages are linked, internally and externally.
The crawlytics.links function gives you a summary of the links, that is similar to
the format of the crawlytics.images DataFrame.
>>> link_df = adv.crawlytics.links(crawldf, internal_url_regex='nytimes.com')
>>> link_df
url |
link |
text |
nofollow |
internal |
|
|---|---|---|---|---|---|
0 |
Skip to content |
False |
True |
||
0 |
Skip to site index |
False |
True |
||
0 |
SKIP ADVERTISEMENT |
False |
True |
||
1 |
https://www.nytimes.com/newsletters/morning-briefing-europe#site-content |
Skip to content |
False |
True |
|
1 |
https://www.nytimes.com/newsletters/morning-briefing-europe#site-index |
Skip to site index |
False |
True |
|
1 |
False |
True |
|||
2 |
https://www.nytimes.com/newsletters/australia-letter#site-content |
Skip to content |
False |
True |
|
2 |
https://www.nytimes.com/newsletters/australia-letter#site-index |
Skip to site index |
False |
True |
|
2 |
False |
True |
|||
3 |
https://www.nytimes.com/newsletters/the-interpreter#site-content |
Skip to content |
False |
True |
|
3 |
https://www.nytimes.com/newsletters/the-interpreter#site-index |
Skip to site index |
False |
True |
|
3 |
False |
True |
|||
4 |
https://www.nytimes.com/section/world/middleeast#site-content |
Skip to content |
False |
True |
|
4 |
Skip to site index |
False |
True |
||
4 |
Middle East |
False |
True |
Every link is represented on a separate row, and we have a few attributes for each link, it's text, whether or not it has a nofollow rel attribute, and optionally whether or not it is internal. For the optional internal parameter you will have to supply a regex to define what internal really means. You could include certain sub-domains, or even consider other domains as part of your same property, and thus they would be considered "internal".
We can now easily count how many links we have per URL, the most frequently used link text, and so on.
We now take a look at redirects.
Analyzing the redirects of a crawled website
Like images and links, the information about redirects is presented using a group of columns:
>>> redirect_df = adv.crawlytics.redirects(crawldf)
>>> redirect_df
url |
status |
order |
type |
download_latency |
redirect_times |
|
|---|---|---|---|---|---|---|
0 |
301 |
1 |
requested |
0.220263 |
1 |
|
0 |
200 |
2 |
crawled |
0.220263 |
1 |
|
26 |
301 |
1 |
requested |
0.079844 |
1 |
|
26 |
403 |
2 |
crawled |
0.079844 |
1 |
|
105 |
301 |
1 |
requested |
0.0630789 |
1 |
|
105 |
403 |
2 |
crawled |
0.0630789 |
1 |
|
218 |
https://nytimes.com/spotlight/privacy-project-data-protection |
301 |
1 |
requested |
0.852014 |
1 |
218 |
https://www.nytimes.com/spotlight/privacy-project-data-protection |
200 |
2 |
crawled |
0.852014 |
1 |
225 |
https://nytimes.com/spotlight/privacy-project-regulation-solutions |
301 |
1 |
requested |
0.732559 |
1 |
310 |
301 |
1 |
requested |
0.435062 |
2 |
|
310 |
301 |
2 |
intermediate |
0.435062 |
2 |
|
310 |
200 |
3 |
crawled |
0.435062 |
2 |
Here each redirect is represented using a group of columns, as well as a group of rows. Columns show attributes of a redirect (status code, the order of the URL in the redirect, the type of the URL in the redirect context, download latency in seconds, and the number of redirects in this specific process). Since a redirect contains multiple URLs, each one of those URLs is represented on its own row. You can use the index of this DataFrame to connect a redirect back to the crawl DataFrame in case you want more context about it.
Let's now see what can be done with large crawl files.
Handling very large crawl files
Many times you might end up crawling a large website, and the crawl file file might be as large as your memory (or even more), making it impossible to analyze.
We have several options availablel to us:
Read a subset of columns
Convert the jsonlines file to parquet
Explore the available column names and their respective data types of a parquet file
The jl_subset function only reads the column subset that you want, massively
reducing the memory consumption of our file.
In some cases you only want a small set of columns, you can read the DataFrame with the
columns of interest, write them to a new file, and delete the old large crawl file.
>>> crawl_subset = adv.crawlytics.jl_subset(
... filepath='/path/to/output_file.jl',
... columns=[col1, col2, ...],
... regex=column_regex)
You can use the columns parameter to specify exactly which columns you want. You can
also use a regular expression to specify a set of columns. Here are some examples of
regular expressions that you might typically want to use:
"img_": Get all image columns, including all availabe <img> attributes.
"jsonld_": Get all JSON-LD columns.
"resp_headers_": Response headers.
"request_headers_": Request headers.
"h\d": Heading columns, h1..h6.
"redirect_": Columns containing redirect information.
"links_": Columns containing link information.
An important characteristic of these groups of columns is that you most likely don't know how many they are, and what they might include, so a regular expression can save a lot of time.
You can use the columns and regex parameters together or either one of them on its own depending on your needs.
Compressing large crawl files
Another strategy while dealing with large jsonlines (.jl) files is to convert them to the highly performant .parquet format. You simply have to provide the current path to the .jl file, and provide a path for the desired .parquet file:
>>> adv.crawlytics.jl_to_parquet("output_file.jl", "output_file.parquet")
Now you have a much smaller file on disk, and you can use the full power of parquet to efficiently read (and filter) columns and rows. Check the`pandas.read_parquet <https://pandas.pydata.org/docs/reference/api/pandas.read_parquet.html>`_ documentation for details.
Exploring the columns and data types of parquet files
Another simple function gives us a DataFrame of the available columns in a parquet file. One of the main advantags of using parquet is that you can select which columns you want to read.
>>> adv.crawlytics.parquet_columns('output_file.parquet') # first 15 columns only
column |
type |
|
|---|---|---|
0 |
url |
string |
1 |
title |
string |
2 |
meta_desc |
string |
3 |
viewport |
string |
4 |
charset |
string |
5 |
h1 |
string |
6 |
h2 |
string |
7 |
h3 |
string |
8 |
canonical |
string |
9 |
alt_href |
string |
10 |
alt_hreflang |
string |
11 |
og:url |
string |
12 |
og:type |
string |
13 |
og:title |
string |
14 |
og:description |
string |
Check how many columns we have of each type.
>>> adv.crawlytics.parquet_columns('nyt_crawl.parquet')['type'].value_counts()
type |
count |
|
|---|---|---|
0 |
string |
215 |
1 |
double |
22 |
2 |
list<element: string> |
5 |
3 |
int64 |
4 |
4 |
list<element: struct<@context: string, @type: string, position: int64, url: string>> |
2 |
5 |
list<element: struct<@context: string, @type: string, contentUrl: string, creditText: string, url: string>> |
2 |
6 |
list<element: struct<@context: string, @type: string, caption: string, contentUrl: string, creditText: string, height: int64, url: string, width: int64>> |
1 |
7 |
timestamp[ns] |
1 |
8 |
list<element: struct<@context: string, @type: string, item: string, name: string, position: int64>> |
1 |
9 |
list<element: struct<@context: string, @type: string, name: string, url: string>> |
1 |
Module functions
- images(crawldf)[source]
Summarize crawled images from a crawl DataFrame.
- Parameters:
crawldf (pandas.DataFrame) -- A crawl DataFrame as a result of the advertools.crawl function.
- Returns:
img_summary -- A DataFrame containing all available img tags and their attributes mapped to their respective URLs where each image data is represented with a separate row.
- Return type:
pandas.DataFrame
Examples
>>> import advertools as adv >>> import pandas as pd >>> crawldf = pd.read_json('output_file.jl', lines=True) >>> image_df = adv.crawlytics.images(crawldf) >>> image_df
url
img_src
img_alt
img_loading
img_sizes
img_decoding
img_width
img_height
img_border
0
/vi-assets/static-assets/icon-the-morning_144x144-b12a6923b6ad9102b766352261b1a847.webp
The Morning Logo
nan
nan
nan
nan
nan
0
/vi-assets/static-assets/icon-the-upshot_144x144-0b1553ff703bbd07ac8fe73e6d215888.webp
The Upshot Logo
nan
nan
nan
nan
nan
0
The Daily Logo
nan
nan
nan
nan
nan
1
https://static.nytimes.com/email-images/NYT-Newsletters-Europe-Icon-500px.jpg
morning briefing
nan
nan
nan
nan
nan
nan
2
https://static.nytimes.com/email-images/NYT-Newsletters-AustraliaLetter-Icon-500px.jpg
australia-letter
nan
nan
nan
nan
nan
nan
3
https://static.nytimes.com/email-images/NYT-Newsletters-SONL-TheInterpreter-Icon-500px.jpg
the interpreter
nan
nan
nan
nan
nan
nan
4
nan
(min-width: 1024px) 205px, 150px
async
150
100
nan
4
nan
(min-width: 1024px) 205px, 150px
async
150
100
nan
4
nan
(min-width: 1024px) 205px, 150px
async
150
100
nan
- jl_subset(filepath, columns=None, regex=None, chunksize=500)[source]
Read a jl file extracting selected columns and/or columns matching regex.
- Parameters:
filepath (str) -- The path of the .jl (jsonlines) file to read.
columns (list) -- An optional list of column names that you want to read.
regex (str) -- An optional regular expression of the pattern of columns to read.
chunksize (int) -- How many rows to read per chunk.
Examples
>>> import advertools as adv
Read only the columns "url" and "meta_desc":
>>> adv.crawlytics.jl_subset('output_file.jl', columns=['url', 'meta_desc'])
Read columns matching the regex "jsonld":
>>> adv.crawlytics.jl_subset('output_file.jl', regex='jsonld')
Read the columns "url" and "meta_desc" as well as columns matching "jsonld":
>>> adv.crawlytics.jl_subset('output_file.jl', columns=['url', 'meta_desc'], regex='jsonld')
- Returns:
df_subset -- A DataFrame containing the list of columns and/or columns matching regex.
- Return type:
pandas.DataFrame
- jl_to_parquet(jl_filepath, parquet_filepath)[source]
Convert a jsonlines crawl file to the parquet format.
- Parameters:
jl_filepath (str) -- The path of an existing .jl file.
parquet_fileapth (str) -- The pather where you want the new file to be saved.
Examples
>>> import advertools as adv >>> adv.crawlytics.jl_to_parquet("output_file.jl", "output_file.parquet")
- links(crawldf, internal_url_regex=None)[source]
Summarize links from a crawl DataFrame.
- Parameters:
crawldf (DataFrame) -- A DataFrame of a website crawled with advertools.
internal_url_regex (str) -- A regular expression for identifying if a link is internal or not. For example if your website is example.com, this would be "example.com".
- Returns:
link_df
- Return type:
pandas.DataFrame
Examples
>>> import advertools as adv >>> import pandas as pd >>> crawldf = pd.read_json('output_file.jl', lines=True) >>> link_df = adv.crawlytics.links(crawldf) >>> link_df
url
link
text
nofollow
internal
0
Skip to content
False
True
0
Skip to site index
False
True
0
SKIP ADVERTISEMENT
False
True
1
https://www.nytimes.com/newsletters/morning-briefing-europe#site-content
Skip to content
False
True
1
https://www.nytimes.com/newsletters/morning-briefing-europe#site-index
Skip to site index
False
True
1
False
True
2
https://www.nytimes.com/newsletters/australia-letter#site-content
Skip to content
False
True
2
https://www.nytimes.com/newsletters/australia-letter#site-index
Skip to site index
False
True
2
False
True
- parquet_columns(filepath)[source]
Get column names and datatypes of a parquet file.
- Parameters:
filepath (str) -- The path of the file that you want to get columns names and types.
- Returns:
columns_types -- A DataFrame with two columns "column" and "type".
- Return type:
pandas.DataFrame
- redirects(crawldf)[source]
Create a tidy DataFrame for the redirects in crawldf with the columns:
url: All the URLs in the redirect (chain).
status: The status code of each URL.
type: "requested", "inermediate", or "crawled".
order: 1, 2, 3... up to the number of urls in the redirect chain.
redirect_times: The number of redirects in the chain (URLs in the chain minus one).
- Parameters:
crawldf (pandas.DataFrame) -- A DataFrame of an advertools crawl file
Examples
>>> import advertools as adv >>> import pandas as pd >>> crawldf = pd.read_json('output_file.jl', lines=True) >>> redirect_df = adv.crawlytics.redirects(crawldf) >>> redirect_df
url
status
order
type
download_latency
redirect_times
0
301
1
requested
0.220263
1
0
200
2
crawled
0.220263
1
26
301
1
requested
0.079844
1
26
403
2
crawled
0.079844
1
105
301
1
requested
0.0630789
1
105
403
2
crawled
0.0630789
1