Tutorial by Examples: ce

You are allowed to implement custom exceptions that can be thrown just like any other exception. This makes sense when you want to make your exceptions distinguishable from other errors during runtime. In this example we will create a custom exception for clear handling of problems the application ...

Itertools "islice" allows you to slice a generator: results = fetch_paged_results() # returns a generator limit = 20 # Only want the first 20 results for data in itertools.islice(results, limit): print(data) Normally you cannot slice a generator: def gen(): n = 0 wh...

If your code encounters a condition it doesn't know how to handle, such as an incorrect parameter, it should raise the appropriate exception. def even_the_odds(odds): if odds % 2 != 1: raise ValueError("Did not get an odd number") return odds + 1

Use try...except: to catch exceptions. You should specify as precise an exception as you can: try: x = 5 / 0 except ZeroDivisionError as e: # `e` is the exception object print("Got a divide by zero! The exception was:", e) # handle exceptional case x = 0 final...

Sometimes you want to catch an exception just to inspect it, e.g. for logging purposes. After the inspection, you want the exception to continue propagating as it did before. In this case, simply use the raise statement with no parameters. try: 5 / 0 except ZeroDivisionError: print(&quo...

In the process of handling an exception, you may want to raise another exception. For example, if you get an IOError while reading from a file, you may want to raise an application-specific error to present to the users of your library, instead. Python 3.x3.0 You can chain exceptions to show how t...

Exception handling occurs based on an exception hierarchy, determined by the inheritance structure of the exception classes. For example, IOError and OSError are both subclasses of EnvironmentError. Code that catches an IOError will not catch an OSError. However, code that catches an EnvironmentErr...

Exceptions are just regular Python objects that inherit from the built-in BaseException. A Python script can use the raise statement to interrupt execution, causing Python to print a stack trace of the call stack at that point and a representation of the exception instance. For example: >>&gt...

To install package from local source file: install.packages(path_to_source, repos = NULL, type="source") install.packages("~/Downloads/dplyr-master.zip", repos=NULL, type="source") Here, path_to_source is absolute path of local source file. Another command that ...

Inspecting system resource usage is an efficient way to find misbehaving applications. This example is an equivalent of the traditional top command for containers: docker stats To follow the stats of specific containers, list them on the command line: docker stats 7786807d8084 7786807d8085 D...

Inspecting system resource usage is an efficient way to narrow down a problem on a live running application. This example is an equivalent of the traditional ps command for containers. docker top 7786807d8084 To filter of format the output, add ps options on the command line: docker top 7786807...

We will model the process #Load the forecast package library(forecast) #Generate an AR1 process of length n (from Cowpertwait & Meltcalfe) # Set up variables set.seed(1234) n <- 1000 x <- matrix(0,1000,1) w <- rnorm(n) # loop to create x for (t in 2:n) x[t] <- 0.7...

Sometimes you want to do something with the exception you catch (like write to log or print a warning) and let it bubble up to the upper scope to be handled. To do so, you can rethrow any exception you catch: try { ... // some code here } catch (const SomeException& e) { std::cout &l...

A type that conforms to the SequenceType protocol can iterate through it's elements within a closure: collection.forEach { print($0) } The same could also be done with a named parameter: collection.forEach { item in print(item) } *Note: Control flow statements (such as break or continu...

if ([object respondsToSelector:@selector(someOptionalMethodInProtocol:)]) { [object someOptionalMethodInProtocol:argument]; }

Due to Node's asynchronous nature, creating or using a directory by first: checking for its existence with fs.stat(), then creating or using it depending of the results of the existence check, can lead to a race condition if the folder is created between the time of the check and the time of ...

The nodemon package makes it possible to automatically reload your program when you modify any file in the source code. Installing nodemon globally npm install -g nodemon (or npm i -g nodemon) Installing nodemon locally In case you don't want to install it globally npm install --save-dev nodemo...

Given a sequence of steps we use repeatedly, it's often handy to store it in a function. Pipes allow for saving such functions in a readable format by starting a sequence with a dot as in: . %>% RHS As an example, suppose we have factor dates and want to extract the year: library(magrittr) ...

This topic specifically talks about UTF-8 and considerations for using it with a database. If you want more information about using databases in PHP then checkout this topic. Storing Data in a MySQL Database: Specify the utf8mb4 character set on all tables and text columns in your database. ...

Trailing spaces \s*$: This will match any (*) whitespace (\s) at the end ($) of the text Leading spaces ^\s*: This will match any (*) whitespace (\s) at the beginning (^) of the text Remarks \s is a common metacharacter for several RegExp engines, and is meant to capture whitespace characters (...