The concept of Null Reference is sometimes referred to as “The Billion Dollar Mistake”. In keeping with modern best practices, you want to eliminate null values from your code.
We begin with the following general rules regarding the use of null values in Scala code:
Stream API was introduced in Java 8. It provided a declarative programming approach to iterate and perform operations over a collection. Until Java 7, for and for each were the only options available, which was an imperative programming approach. In this article I will introduce you to the Stream API and how it provides an abstraction over the common operations performed over a collection.
According to Stack Overflow, Python is the fastest growing programming language. Netflix uses Python, IBM uses Python, and hundreds of other companies all use Python. Let’s not forget Dropbox. Dropbox is also created in Python.
Some of the advantages Python offers when compared to other programming languages are:
When you need to concatenate a list of strings, you can do this using a for loop by adding each element one by one. However, this would be very inefficient, especially if the list is long. In Python, strings are immutable, and thus the left and right strings would have to be copied into the new string for every pair of concatenation.
A better approach is to use the join() function as shown below:
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characters = ['p', 'y', 't', 'h', 'o', 'n'] word = "".join(characters) print(word) # python |
Suppose you were given a task to combine several lists with the same length and print out the result? Again, here is a more generic way to get the desired result by utilizing zip()as shown in the code below:
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countries = ['France', 'Germany', 'Canada'] capitals = ['Paris', 'Berlin', 'Ottawa'] for country, capital in zip(countries,capitals): print(country, capital) # France Paris Germany Berlin Canada Ottawa |
The Python itertools module is a collection of tools for handling iterators. itertools has multiple tools for generating iterable sequences of input data. Here I will be using itertools.combinations() as an example. itertools.combinations() is used for building combinations. These are also the possible groupings of the input values.
Let’s take a real world example to make the above point clear.
Suppose there are four teams playing in a tournament. In the league stages every team plays against every other team. Your task is to generate all the possible teams that would compete against each other.
Let’s take a look at the code below:
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import itertools friends = ['Team 1', 'Team 2', 'Team 3', 'Team 4'] list(itertools.combinations(friends, r=2)) # [('Team 1', 'Team 2'), ('Team 1', 'Team 3'), ('Team 1', 'Team 4'), ('Team 2', 'Team 3'), ('Team 2', 'Team 4'), ('Team 3', 'Team 4')] |
Let’s say we have two lists, one list contains names of the students and second contains marks scored by them. Let’s see how we can convert those two lists into a single dictionary. Using the zip function, this can be done using the code below:
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students = ["Peter", "Julia", "Alex"] marks = [84, 65, 77] dictionary = dict(zip(students, marks)) print(dictionary) # {'Peter': 84, 'Julia': 65, 'Alex': 77} |
Python has the ability to return multiple values from a function call, something missing from many other popular programming languages. In this case the return values should be a comma-separated list of values and Python then constructs a tuple and returns this to the caller. As an example see the code below:
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def multiplication_division(num1, num2): return num1*num2, num1/num2 product, division = multiplication_division(15, 3) print("Product=", product, "Quotient =", division) # Product= 45 Quotient = 5.0 |
Sorting any sequence is very easy in Python using the built-in method sorted()which does all the hard work for you. sorted()sorts any sequence (list, tuple) and always returns a list with the elements in sorted manner. Let’s take an example to sort a list of numbers in ascending order.
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sorted([3,5,2,1,4]) # [1, 2, 3, 4, 5] |
Taking another example, let’s sort a list of strings in descending order.
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sorted(['france', 'germany', 'canada', 'india', 'china'], reverse=True) # ['india', 'germany', 'france', 'china', 'canada'] |
With new functional features adding up in languages like java, it is good to know how to loop in a functional way. Following are some of functional alternative for ‘for’ loop which you can use