Dealing with Python Reactively - PyCon Korea 2017
3 likes1,198 views
The document discusses reactive programming and its principles, emphasizing asynchronous data flow and the concept of observables using reactive extensions (RxPy). It explains coroutines and generators in Python, highlighting their differences and use cases, particularly in managing and processing data efficiently. The content includes code examples to illustrate the principles and functionalities of reactive programming and coroutine usage.
Dealing with Python Reactively - PyCon Korea 2017
- 1. Dealing with Python Reactively PyCon Korea 2017 Kenneth
- 3. INTRODUCTION Ractive Progamming RxPy Coroutine / Generator CH1. CH2. CH3.
- 5. What is reactive programming? CH 1. Reactive Programming The new paradigm that focused on the asynchronous data flow
- 6. Difficult
- 7. Key keyword #1 CH 1. Reactive Programming Asynchronous It can be received the data that is not guaranteed In the asynchronous environment sequentially, And also it can be processed the data flexible.
- 8. Key keyword #2 CH 1. Reactive Programming Reactive It is not executed if there is no operation (input) from the outside.
- 9. Key keyword #3 CH 1. Reactive Programming Lightweight Data flow can be subdivided for each purpose, And also it can be merged again. This makes it possible to reduce the weight.
- 10. The data flows. CH 1. Reactive Programming
- 11. However it does not flow at the same time. So we can not guarantee that the data always comes. CH 1. Reactive Programming
- 12. It can not be easy to process the data that comes every another times. CH 1. Reactive Programming .next() .subscribe()
- 13. Controlling multiple data flows. Reactive programming makes it possible. CH 1. Reactive Programming The data that comes from each different times concurrently, To be sequentially
- 14. It only see the data flows. That’s why it’s intuitive. CH 1. Reactive Programming Map Filter Merge Reduce On Complete On Error Retry Skip Buffer
- 15. CH2. RxPy
- 16. ReactiveX (RX) CH 2. RxPy Microsoft announced `Volta` project in 2007 It is officially known as `Reactive Extensions` in 2009 It was gradually released as open source since 2012
- 17. def observer_generator(observer): # It passes the string “hello” through the observer. observer.on_next("hello") # Likewise, it passes the string "world!" through the observer. observer.on_next("world!") def main(): # Create an observer, passes it to a predefined function, and receives an object that can receive it. observable = Observable.create(observer_generator) # Receive the observer, At this time the observer read the variable that passed at on_next. # Oh! After the below subscribe is started, the above observer_generator will be executed. observable.subscribe(on_next=lambda value: print(value)) hello_world.py observable.create (Create an observer) observer_generator observer
- 18. def observer_generator(observer): # It passes the string “hello” through the observer. observer.on_next("hello") # Likewise, it passes the string "world!" through the observer. observer.on_next("world!") def main(): # Create an observer, passes it to a predefined function, and receives an object that can receive it. observable = Observable.create(observer_generator) # Receive the observer, At this time the observer read the variable that passed at on_next. # Oh! After the below subscribe is started, the above observer_generator will be executed. observable.subscribe(on_next=lambda value: print(value)) hello_world.py observable 1. next(‘hello’) 2. next(‘world!’) observer 1. print(‘hello’) 2. print(‘world!’) It passes the data through on_next Print the message that received from on_next
- 19. from rx import Observable, Observer class PrintObserver(Observer): def on_next(self, value): print('on_next value:%s’ % (value)) def on_completed(self): print('on_completed !') def on_error(self, value): print('on_error value:%s’ % (value)) def observer_generator(observer): observer.on_next(“break") observer.on_next(“the ice!") while True: message = input() if message: observer.on_next(message) else: observer.on_completed() break def main(): observable = Observable.create(observer_generator) observable.subscribe(PrintObserver()) ice_breaking.py Observable (Data forwarder) Observable (Data receiver) subscribe() next(‘break’) next(‘the ice!’) next(‘message’) print() print() print() on_next on_next on_next completed() on_completed print() 1. You can expand incoming messages by using Predefined object in Subscribe method.
- 21. Coroutine? CH 3. Coroutine / Generator Unlike functions, Routines whose parents are “equivalent” to the called function. Python only: Coroutine can process only the received data.
- 22. Coroutine vs General routine CH 3. Coroutine / Generator General Routine Function call Return Parameters Result Coroutine Function call Parameters Yield Yield Yield Main code Main code Calculating Calculating Calculating Send Send Send
- 23. Use Case CH 3. Coroutine / Generator Init Data Caller Coroutine 2. Wait for the caller's input via yield (Will be returned to caller code lines) 1. Inserting initial data to apply to coroutines 3. If you have input to the caller, return to the coroutine code and execute the logic. If yield appearsin the logic, it returns to the parent code again. (repeat) next() Yield Yield 4. Finally, the caller ends the coroutine. Close
- 24. Generator? CH 3. Coroutine / Generator If Coroutine is a gourmand, The Generator is the giving tree. A generator is a `generator` that generates data through yield.
- 25. Do you know range function? CH 3. Coroutine / Generator def main(): # Use the range function to insert each value from 0 to 2 # into value and repeat it three times. for value in range(3): print(u’current value %d' % (value)) OUTPUT: current_value 0 current_value 1 current_value 2
- 26. Making range function by using Generator. CH 3. Coroutine / Generator # It is the range function created by using the Generator. def custom_range(number): index = 0 while(index < number): # At this point, we go back to the parent that called this function, # Pass the value, and proceed to the parent's logic until we call this function again. # This is the heart of the generator. Remember this! yield index index += 1
- 27. coroutine_generator.py def main(): # Let's try to use the existing range function. for value in range(3): print(u'original range %d' % (value)) # Insert a line escaping for the division. print(u'n') # Let's try the function we just created. for value in custom_range(3): print(u'custom range %d' % (value)) OUTPUT original range 0 original range 1 original range 2 custom range 0 custom range 1 custom range 2
- 28. Use Case CH 3. Coroutine / Generator Large Data Memory Process yield 1. In a real-time cursor, yield returns every 500 datasets. 2. Actually there are only 500 data in memory, so there is out of memory problem. 3. When 500 data are processed and the process is finished, 500 data will be emptied from the memory. Likewise, there is no out of memory problem. 4. At the end of the process, it again gets 500 data from Large Data.
- 29. Conclusion about Generator CH 3. Coroutine / Generator Data that comes in real time can be used to stabilize the memory by using the generator! (Performance difference is insignificant)
- 30. What is the difference Between Coroutine and Generator? CH 3. Coroutine / Generator Corutine Function call Parameters Yield Yield Yield Main code Calculating Calculating Calculating Send Send Generator Function call Parameters Yield Yield Yield Main code Calculating Calculating Calculating Return Return Return Send
- 31. Question