10 Python one liners you’ll actually use

Key Takeaways

In this video, you'll learn 10 Python oneliners, which are essentially small Python snippets that are extremely useful, allow you to write better and more efficient code, and will demonstrate that you know Python better than most other people. So, with that said, let's get into it and start with snippet number one. The first oneliner on my list is the following, which allows you to flatten a nested list. Now, this involves using nested for loops to iterate through all of the different objects inside of some kind of structure and flatten them. So here's the snippet right here. You can modify it of course, but just note that you can create a list comprehension, which is essentially a for loop inside of a list like this. In this case, we've done two for loops. So we have every item for sublist in nested for item in sublist. So we're looping through the entire structure. Then we're looping through each item in the substructure and create creating an item for that story in this flattened list. If you have a quick look at an example here, you can see that if we have a matrix, we can flatten it quite easily by using this. So we get the following result. And if we look at something where we don't have even elements, right? So maybe A, B, C, D, E, F, something like that. Same thing. We don't need to know the size of the structure. We can flatten it by using this. So if I run the code here, you can take a quick look at the output where you can see that we get the flattened list. The next snippet on my list allows you to swap two variables or actually any number of variables in place. So quite often we want to swap the two values of variables. And in Python, you can actually just do that in one single line. So you can write something like a comma b equals b comma a. The reason this is quite useful is because normally if you wanted to swap values you would need to write something like I have in the demo. So you would say something like temporary equals a a is equal to b and then b is equal to temp and you've kind of unnecessarily created this variable and you've used three lines to perform the swap. And of course this gets even more complicated if you want to swap multiple values. So you can simply write them separated by commas. And you can see that we can do a basic swap like so or even a swap using array elements. In fact, this syntax actually works with almost all different types of Python objects. And if I just quickly run the code here, you can see that of course we get the correct values where they've been swapped. But if we wanted to, we could even add something additional like we could say ar at 2 is equal to and then whatever value we want. It doesn't really make sense here, but we could do something like, you know, array at zero. And if we run this right here, you'll see that again this still works. So you can do multiple elements again all in one line without having to create any temporary variables. The next oneliner on my list is the following which allows you to read a file into a list of lines. Now I use this quite frequently. I'm always opening up different text files, JSON files, etc. and needing to read them. Now you can manually parse the file if you would like, but you can also use this fancy split lines method, which is really why I'm showing you this snippet. So what does this do? It opens a file, reads all the content, and splits it based on the new line characters. So, this also avoids keeping the back slashn character at the end of each line, which is commonly something you need to parse out when you're dealing with files. Now, this is useful for config files, log files, etc. And as it says here, if you using this in production, then you would open the file using the context manager. But it doesn't matter. I'm just showing you how it works here. So, you can see that we can import something like path lib. We can write some text into a file, and then we can open it up with the split lines method. And when we do that, we get all of the lines cleanly inside of this list without any of the new line characters. Moving on, the next oneliner I have for you has to do with the counter object from the collections module in Python. If you're not familiar, Python has a built-in module called collections, which is extremely useful and contains all kinds of different classes and objects. One of which is the counter, which allows you to automatically count different structures in Python. Now, while this is two lines, really, the one line is this. after you import the counter from collections. And let me quickly show you what it does. So you can see that if we have a bunch of different values here, a common thing we may want to do is count the frequency of those. Now, in order to count the frequency, we could write a for loop, loop through it, you know, create a dictionary, for example, and set all of the values. Or we can simply use this counter from the collections module. When we do that, it will actually return to us a counter object, which is very similar to a dictionary that contains all of the keys, which are the values inside of the list, as well as their frequency or the number of times that they occur. And then we can use methods like most common. And this gives us the first most common element or the second most common element. And there's a lot of other useful methods there as well. So if I clean this up and just run this code, you can see that we get the counter object like so. You can see we get another counter down here. In order to use the counter, you do need a list. So in this case, what we have is the cat sat on the mat. We split that into a list based on the spaces. And then you can see it gives us the frequency of the words rather than just each individual letter. Extremely useful. A lot of other stuff comes from the collections module. So make sure you check it out. Now, quick pause because if you're watching this video, you're clearly interested in Python. And if you want to go way deeper than just oneliners in this video, then you need to check out this completely free event which is Python Unplugged by Jetrains. Now, it's a completely free online Python conference that's happening March 4th from 11:00 a.m. to 6:30 p.m. Central time. So, you can literally watch it from your couch for free. Now, the lineup they've got for speakers is pretty stacked. You've got Carol Willing, who's a core developer on Jupiter Lab. You have Travis Olafont, not sure if I'm saying that name correctly, who's the co-creator of NumPy and basically one of the reasons that Python is dominant in data science. And you have Sheena Okonnell, who's doing really interesting work in Python education. Now, the topics cover everything from AI and data science to web development, open- source, core Python, and really the whole Python ecosystem and where it's headed. So, whether you're getting into Python or you've been writing it for years, there's something in there for you. And again, this is free, it's online, and I'll drop the link in the description so you can register. Big shout out to Jet Brains for being a long-term partner of this channel and making us aware of opportunities like this. Again, link in the description. Now, let's get back to the Python oneliners. Now the next oneliner that I have may seem pretty basic but I use it all the time and this is reversing a string or any iterable object or sequence. Now in order to do that you can simply use the colon negative1 inside of the indicy or index operator whatever you'd like to call it. And the way that this works is that you're using something called a slice in Python. And the slice looks like this. Start stop and then step. But if you don't include the start and the stop value and you just include a step value of negative one, effectively what this ends up doing is just reversing the entire sequence. So it means start at the beginning, stop at the end and then step by one, which means go in reverse. So you end up getting a reversed sequence. Anyways, I'll show you what I mean. If we have a look at radar and we run this, we'll see that it's equal to the same if we reverse it. The reason for that is that it's a palendrome. So we could check if something's a palendrome using this. We also could just reverse something. So if I run this here, you'll see that we get the reverse string. This works on numbers. It doesn't need to be a string. It works on lists. Really, anything that has some kind of order and that is an iterable object in Python, you can run this slice operator on. So now we move on to conditional assignment. This is essentially an inline if or else statement. This is very useful when you want to write a short condition in a single line and have it equal to some kind of variable. This just cleans up the code, makes it a little bit easier for you to see and can also be used inside of things like list comprehensions where you're writing in a single line. So you can see that you can write something like even if some condition is true otherwise the result. So essentially whatever you want to have on the left if something is true and then otherwise you have the other option. Again this is an inline if or conditional assignment like so. So for example we could label something as even or odd. So x is equal to 4. The result is even if x mod 2 is equal to zero otherwise odd. We could take a min, max or default value. So clamping some particular value. So score if less than 100 otherwise 100 plus right and it just saves us a few lines of code it makes the code a lot easier to read. Now the next oneliner is similar and something a lot of people don't actually know that you can do in python and that is to write a chained comparison. So if you have a look at this quick example here, if you wanted to compare if a was less than b and b was less than c, what you would need to do typically is write this compound condition like this where you have a less than b and b less than c. And these are two separate conditions. Now this works. It's totally fine. However, if you just want to write it a little bit cleaner, you can write something like this. So if you want to see if one particular value is between two values, you can simply just say if one is less than x, which is less than 10. And this allows you to check it without writing two separate conditions and is a little bit more clear to read. So you can see if a number is within some range. And then you could also do something like check multiple conditions. You know is i less than zero and is i less than n. So if we run this you can see that this works and it's valid syntax. Now the next oneliner allows you to create a commaepparated string from any list or iterable object. Now this is by using the dotjoin method as you can see right here. The way the dot join works is you take some kind of delimiter or separator. So in this case we have a comma and a space and then you join in a bunch of objects from a list into it. What this will do is it will create a new string that contains all of the values in whatever you've put here. So whatever like the list is that you've put here separated by this. So separated by a string or separated by a pipe or an a or a dash or whatever it is you want to separate it by. Now the reason why I've used the map here is because we might have some values that aren't a string inside of our list and if we want to join them we do need to have strings. So what we could do is we could map all of the values from some list to the string function. This means it's going to convert it into a string. Then we pass this list of strings and join them together using the comma. So you can see we could take a list of numbers and we could combine them together with the comma. So if I run this, you see we get 1 2 3 4. If we change this to something like a pipe, you can see now we get them separated with a pipe. If we add another value, now we get them spaced out. And then same thing down here. If we already have strings then we could just join them together without using the map function. Now the next oneliner I have for you is an absolute essential and this is pretty printing any nested structure. Now in Python there is this print module. It allows you to bring in the print function. Print stands for pretty printing and what this will do is give you a nicely formatted object so that you can read it a lot more easily if you're printing it out to the terminal or the console. And this is especially useful when you're working with API requests or API responses, sorry, or anything that's just very kind of difficult to parse without having it in the correct format. So for example, we might have this large JSON object that we receive. Now before we pretty it, let's just print it normally so you can see what it looks like. So if I just print out the data and I run this cell, you see that we just kind of get it in one line and it's practically impos impossible sorry to read. Whereas if we print it, so let's do it like this and we run the code. You can see they will automatically format it for us. And we can also specify parameters like the depth. So the number of levels that we want to print out as well as if we have a look here the indentation, the width, compact, all of that kind of stuff. So that you can read it in the terminal a lot easier. Very easy. Just import it for any kind of JSON object you want to parse. All right. And the last oneliner is one of my favorite ones in Python. And this is effectively an Easter egg that was brought into the language that a lot of people don't know about. If you try to import braces from the future module or the dunder future module with two underscores, you're going to see what happens is that it actually gives you a custom exception that says not a chance. Just kind of a fun one. Python actually has a lot of other Easter eggs like this as well. For example, if you wanted to see one, you could try to import the anti-gravity module. And let's just move this and run. And you'll see that what it actually does is it opens up a web page here that gives you a kind of comic about Python, which is funny. And there's a few other Easter eggs as well, but I just want to throw that in at the end to give you guys something to smile at. So, anyways, that is it for this video. If you enjoyed, make sure to leave a like, subscribe, and I will see you in the next one. [music]