Community Data Science Workshops (Fall 2014)/Day 2 lecture: Difference between revisions
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[[File:Highfivekitten.jpeg|200px|thumb|In which you learn how to use Python and web APIs to meet the likes of her!]] |
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== Lecture Slides == |
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* [http://mako.cc/teaching/2014/cdsw-autumn/lecture2-web_apis.pdf Slides (PDF)] — For viewing |
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* [http://mako.cc/teaching/2014/cdsw-autumn/lecture2-web_apis.odp Slides (ODP Libreoffice Slides Format)] — For editing and modification |
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== Resources == |
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* Encoding: |
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** [http://nedbatchelder.com/text/unipain.html Pragmatic Unicode] |
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** [https://docs.python.org/2/howto/unicode.html Official Python Unicode documentation] |
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== Lecture Outline == |
== Lecture Outline == |
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;Introduction and context |
;Introduction and context |
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* You can write some tools in Python now. Congratulations! |
* You can write some tools in Python now. Congratulations! |
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* Today we'll learn how to find/create data sets |
* Today we'll learn how to find/create data sets |
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* Next week we'll get into data science (asking and answering questions) |
* Next week we'll get into data science (asking and answering questions) |
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;Outline: |
;Outline: |
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* What did we learn in Session 1? |
* What did we learn in Session 1? |
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* What is an API? |
* What is an API? |
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* Introduction to structured data (JSON) |
* Introduction to structured data (JSON) |
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* How do we use APIs in general? |
* How do we use APIs in general? |
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;What is a (web) API? |
;What is a (web) API? |
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* API: a structured way for programs to talk to each other (aka an interface for programs) |
* API: a structured way for programs to talk to each other (aka an interface for programs) |
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* Web APIs: like a website your programs can visit (you:a website::your program:a web API) |
* Web APIs: like a website your programs can visit (you:a website::your program:a web API) |
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; How do we use an API to fetch datasets? |
; How do we use an API to fetch datasets? |
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Basic idea: your program sends a request, the API sends data back |
Basic idea: your program sends a request, the API sends data back |
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* Where do you direct your request? The site's API endpoint. |
* Where do you direct your request? The site's API endpoint. |
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* How do you understand (i.e. parse) the data? |
* How do you understand (i.e. parse) the data? |
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** There's a module for that! |
** There's a module for that! |
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; How do we write Python programs that make web requests? |
; How do we write Python programs that make web requests? |
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* the ability to save to files |
* the ability to save to files |
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* the ability to understand (i.e., parse) JSON data that APIs usually give us |
* the ability to understand (i.e., parse) JSON data that APIs usually give us |
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; Session 1 review |
; Session 1 review |
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* Navigating in the terminal and using it to run programs |
* Navigating in the terminal and using it to run programs |
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* Writing Python: |
* Writing Python: |
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; New programming concepts: |
; New programming concepts: |
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* interpolate variables into a string using % and %()s |
* interpolate variables into a string using % and %()s |
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* requests |
* requests |
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* open files and write to them |
* open files and write to them |
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* parsing a string (turning the string into a data structure we can manipulate) |
* parsing a string (turning the string into a data structure we can manipulate) |
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; How do we use an API to fetch kitten pictures? |
; How do we use an API to fetch kitten pictures? |
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[http://placekitten.com/ placekitten.com] |
[http://placekitten.com/ placekitten.com] |
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* API that takes specially crafted URLs and gives appropriately sized picture of kittens |
* API that takes specially crafted URLs and gives appropriately sized picture of kittens |
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** kittens of different sizes |
** kittens of different sizes |
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** kittens in greyscale or color |
** kittens in greyscale or color |
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* Now we write a small program to grab an arbitrary square from placekitten by asking for the size on standard in |
* Now we write a small program to grab an arbitrary square from placekitten by asking for the size on standard in: [http://mako.cc/teaching/2014/cdsw-autumn/placekitten_raw_input.py placekitten_raw_input.py] |
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; Introduction to structured data (JSON, JavaScriptObjectNotation) |
; Introduction to structured data (JSON, JavaScriptObjectNotation) |
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* what is json: useful for more structured data |
* what is json: useful for more structured data |
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* import json; json.loads() |
* import json; json.loads() |
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* can reflect more complicated data structures |
* can reflect more complicated data structures |
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* Example file at http://mako.cc/cdsw.json |
* Example file at http://mako.cc/cdsw.json |
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* download it and parse it |
* download it and parse it: [http://mako.cc/teaching/2014/cdsw-autumn/parse_cdswjson.py parse_cdswjson.py] |
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; Using other APIs |
; Using other APIs |
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* every API is different, so read the documentation! |
* every API is different, so read the documentation! |
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* If the documentation isn't helpful, search online |
* If the documentation isn't helpful, search online |
Latest revision as of 22:05, 15 March 2015
Lecture Slides
- Slides (PDF) — For viewing
- Slides (ODP Libreoffice Slides Format) — For editing and modification
Resources
Lecture Outline
- Introduction and context
- You can write some tools in Python now. Congratulations!
- Today we'll learn how to find/create data sets
- Next week we'll get into data science (asking and answering questions)
- Outline
- What did we learn in Session 1?
- What is an API?
- How do we use one to fetch interesting datasets?
- How do we write programs that use the internet?
- How can we use the placekitten API to fetch kitten pictures?
- Introduction to structured data (JSON)
- How do we use APIs in general?
- What is a (web) API?
- API: a structured way for programs to talk to each other (aka an interface for programs)
- Web APIs: like a website your programs can visit (you:a website::your program:a web API)
- How do we use an API to fetch datasets?
Basic idea: your program sends a request, the API sends data back
- Where do you direct your request? The site's API endpoint.
- For example: Wikipedia's web API endpoint is http://en.wikipedia.org/w/api.php
- How do I write my request? Put together a URL; it will be different for different web APIs.
- Check the documentation, look for code samples
- How do you send a request?
- Python has modules you can use, like
requests
(they make HTTP requests)
- Python has modules you can use, like
- What do you get back?
- Structured data (usually in the JSON format)
- How do you understand (i.e. parse) the data?
- There's a module for that!
- How do we write Python programs that make web requests?
To use APIs to build a dataset we will need:
- all our tools from last session: variables, etc
- the ability to open urls on the web
- the ability to create custom URLS
- the ability to save to files
- the ability to understand (i.e., parse) JSON data that APIs usually give us
- Session 1 review
- Navigating in the terminal and using it to run programs
- Writing Python:
- using variables to manipulate data
- types of data: strings, integers, lists, dictionaries
- if statements
- for loops
- printing
- importing modules, so you can use code other people have written for you!
- New programming concepts
- interpolate variables into a string using % and %()s
- requests
- open files and write to them
- parsing a string (turning the string into a data structure we can manipulate)
- How do we use an API to fetch kitten pictures?
- API that takes specially crafted URLs and gives appropriately sized picture of kittens
- Exploring placekitten in a browser:
- visit the API documentation
- kittens of different sizes
- kittens in greyscale or color
- Now we write a small program to grab an arbitrary square from placekitten by asking for the size on standard in: placekitten_raw_input.py
- Introduction to structured data (JSON, JavaScriptObjectNotation)
- what is json: useful for more structured data
- import json; json.loads()
- like Python (except no single quotes)
- simple lists, dictionaries
- can reflect more complicated data structures
- Example file at http://mako.cc/cdsw.json
- download it and parse it: parse_cdswjson.py
- Using other APIs
- every API is different, so read the documentation!
- If the documentation isn't helpful, search online
- for popular APIs, there are python modules that help you make requests and parse json
Possible issues:
- rate limiting
- authentication
- text encoding issues