You may encounter a special ValueError when working with Python’s math module. Python raises this error when you try to do something that is not mathematically possible or mathematically defined. To understand this error, have a look at the definition of the domain: “The domain of a function is the complete set of possible values … Read more
Why have regular expressions survived seven decades of technological disruption? Because coders who understand regular expressions have a massive advantage when working with textual data. They can write in a single line of code what takes others dozens! This article is all about the re.match() method of Python’s re library. There are two similar methods to … Read more
This chapter from my upcoming book “The Art of Clean Code” (NoStarch 2022) teaches you a well-known but still undervalued idea. The idea is to build a minimum viable product (in short: MVP) to test and validate your hypotheses quickly without losing a lot of time in implementation. In particular, you’ll learn how to apply … Read more
This tutorial explains NumPy’s shape() function. Return the shape of an array or array_like object a. Argument Data Type Description a array_like NumPy array or Python list for which the shape should be returned. If it is a NumPy array, it returns the attribute a.shape. If it is a Python list, it returns a tuple … Read more
Why have regular expressions survived seven decades of technological disruption? Because coders who understand regular expressions have a massive advantage when working with textual data. They can write in a single line of code what takes others dozens! This article is all about the re.fullmatch(pattern, string) method of Python’s re library. There are three similar methods … Read more
The np.polyfit() function, accepts three different input values: x, y and the polynomial degree. Arguments x and y correspond to the values of the data points that we want to fit, on the x and y axes, respectively. The third parameter specifies the degree of our polynomial function. For example, to obtain a linear fit, … Read more
Daily Data Science Puzzle What is the output of this puzzle? Numpy is a popular Python library for data science focusing on linear algebra. This advanced puzzle combines multiple language concepts and numpy features. The topic is a miniature stock analysis of the Apple stock. The puzzle creates a one-dimensional numpy array from raw … Read more
The method re.compile(pattern) returns a regular expression object from the pattern that provides basic regex methods such as pattern.search(string), pattern.match(string), and pattern.findall(string). The explicit two-step approach of (1) compiling and (2) searching the pattern is more efficient than calling, say, search(pattern, string) at once, if you match the same pattern multiple times because it avoids … Read more
Want to calculate the variance of a column in your Pandas DataFrame? In case you’ve attended your last statistics course a few years ago, let’s quickly recap the definition of variance: it’s the average squared deviation of the list elements from the average value. You can calculate the variance of a Pandas DataFrame by using … Read more
Have you ever had a string and wanted to make it a certain length by adding zeros to it? You could type it out. But we’re programmers, we hate typing! Surely there must be a way to code this? To pad zeros to a string, use the str.zfill() method. It takes one argument: the final … Read more
Question: Is it possible to call a function inside a list comprehension statement? Background: List comprehension is a compact way of creating lists. The simple formula is [expression + context]. Expression: What to do with each list element? Context: What elements to select? The context consists of an arbitrary number of for and if statements. … Read more
In many Python regex functions, you see a third argument flags. What are they and how do they work? Flags allow you to control the regular expression engine. Because regular expressions are so powerful, they are a useful way of switching on and off certain features (e.g. whether to ignore capitalization when matching your regex). … Read more