your code in the same way you would if it were synchronous. This is especially important for error handling, since try/except blocks work as you would expect in coroutines while this is difficult to achieve that overrides methods such as write_error and get_current_user and then subclass your own BaseHandler instead of RequestHandler for all your specific handlers. Handling request input The request handler the arguments passed into member variables; it may not produce any output or call methods like send_error. 3. prepare() is called. This is most useful in a base class shared by all of your handler subclasses

main coroutine The Application object Subclassing RequestHandler Handling request input Overriding RequestHandler methods Error Handling Redirection Asynchronous handlers Templates and UI Configuring your code in the same way you would if it were synchronous. This is especially important for error handling, since try/except blocks work as you would expect in coroutines while this is difficult to achieve that overrides methods such as write_error and get_current_user and then subclass your own BaseHandler instead of RequestHandler for all your specific handlers. Handling request input The request handler

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 10.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 29 Handling Operating System Variation 388CONTENTS vi 30 Environment Variables 389 30.1 File locations . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 34.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439 34.4 Exception

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 10.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 29 Handling Operating System Variation 388CONTENTS vi 30 Environment Variables 389 30.1 File locations . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 34.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439 34.4 Exception

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 10.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 29 Handling Operating System Variation 388CONTENTS vi 30 Environment Variables 389 30.1 File locations . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 34.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439 34.4 Exception

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 9.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 9.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 28 Handling Operating System Variation 366 29 Environment Variables 367 29.1 File locations . . . . . . . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 33.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 33.4 Exception

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 9.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 9.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 28 Handling Operating System Variation 366 29 Environment Variables 367 29.1 File locations . . . . . . . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 33.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 33.4 Exception

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 10.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 29 Handling Operating System Variation 391CONTENTS vi 30 Environment Variables 392 30.1 File locations . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448 34.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 34.4 Exception

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 10.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 29 Handling Operating System Variation 391CONTENTS vi 30 Environment Variables 392 30.1 File locations . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448 34.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 34.4 Exception

Evaluation: Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 10.5 Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.6 Tasks (aka Coroutines) C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 29 Handling Operating System Variation 391CONTENTS vi 30 Environment Variables 392 30.1 File locations . Extracting useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448 34.3 Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 34.4 Exception