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While it might seem counterintuitive, you can use logical operators to determine whether or not a statement is run. For instance: File.exist?(filename) or STDERR.puts "#{filename} does not exist!" This will check to see if the file exists and only print the error message if it doesn't....

Say we have the following tree: root - A - AA - AB - B - BA - BB - BBA Now, if we wish to list all the names of the elements, we could do this with a simple for-loop. We assume there is a function get_name() to return a string of the name of a node, a function get_children() t...

If you have your data stored in a list and you want to convert this list to a data frame the do.call function is an easy way to achieve this. However, it is important that all list elements have the same length in order to prevent unintended recycling of values. dataList <- list(1:3,4:6,7:9) ...

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SAS can be run in client-server model, using either the Enterprise Guide thick client or the SAS Studio thin (web-enabled) client, or in "local server" mode where a fully functional SAS system is present on a local machine (Windows or Unix/Linux desktop or server running in interactive mod...

You can create your ssh key using ssh-keygen, it's a program that is part of the ssh installation. To do so just run it and follow the instructions on screen. Here's an example: $ ssh-keygen Generating public/private rsa key pair. The default directory where you ssh key pair will be saved is i...

Ever wanted to call a multicast delegate but you want the entire invokation list to be called even if an exception occurs in any in the chain. Then you are in luck, I have created an extension method that does just that, throwing an AggregateException only after execution of the entire list complete...

Swallowing Exceptions One should always re-throw exception in the following way: try { ... } catch (Exception ex) { ... throw; } Re-throwing an exception like below will obfuscate the original exception and will lose the original stack trace. One should never do this! The st...

Similar to the built-in function zip(), itertools.zip_longest will continue iterating beyond the end of the shorter of two iterables. from itertools import zip_longest a = [i for i in range(5)] # Length is 5 b = ['a', 'b', 'c', 'd', 'e', 'f', 'g'] # Length is 7 for i in zip_longest(a, b): x...

Who says you cannot throw multiple exceptions in one method. If you are not used to playing around with AggregateExceptions you may be tempted to create your own data-structure to represent many things going wrong. There are of course were another data-structure that is not an exception would be mor...

Descriptive statistics (mean, standard deviation, number of observations, minimum, maximum, and quartiles) of numerical columns can be calculated using the .describe() method, which returns a pandas dataframe of descriptive statistics. In [1]: df = pd.DataFrame({'A': [1, 2, 1, 4, 3, 5, 2, 3, 4, 1],...

explode and strstr are simpler methods to get substrings by separators. A string containing several parts of text that are separated by a common character can be split into parts with the explode function. $fruits = "apple,pear,grapefruit,cherry"; print_r(explode(",",$fruits))...

In the app folder find package.json and modify the following line to include the latest version, save the file and close. "react-native": "0.32.0" In terminal: $ npm install Followed by $ react-native upgrade

You can also pattern match on Elixir Data Structures such as Lists. Lists Matching on a list is quite simple. [head | tail] = [1,2,3,4,5] # head == 1 # tail == [2,3,4,5] This works by matching the first (or more) elements in the list to the left hand side of the | (pipe) and the rest of the ...

Keyword lists are tuples of key/value, generally used as options for a function call. [{:a, 1}, {:b, 2}] // creates a non-empty keyword list Keyword lists can have the same key repeated more than once. [{:a, 1}, {:a, 2}, {:b, 2}] [{:a, 1}, {:b, 2}, {:a, 2}] Keys and values can be any type: ...

CountDownLatch A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes. A CountDownLatch is initialized with a given count. The await methods block until the current count reaches zero due to invocations of the count...

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Classpath requirements Eclipselink The Eclipselink and JPA API need to be included. Example Maven dependencies: <dependencies> <dependency> <groupId>org.eclipse.persistence</groupId> <artifactId>eclipselink</artifactId> <version>2.6.3&lt...

Scipy contains parts written in C, C++, and Fortran that need to be compiled before use. Therefore make sure the necessary compilers and Python development headers are installed. Having compiled code also means that Scipy needs additional steps to import from development sources, which are explained...