freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. If we change the order of the arguments, we get the exact same result: Now let's talk a little bit about the return value of this method. Tip: The same happened with "A" and "B" (length 1) and "AAA" and "BBB" (length 3), their original order relative to each other was preserved. One amazing feature of the Linux operating system is the Command Line Interface (CLI) which allows users to interact with their computer from a shell. The reverse () method reverses the sorting order of the elements. a. sort() b. map() c. splice() d. find() In Linux, anything that begins with a . Basically, this is used to remind us that we are modifying the original list in memory, not generating a new copy of the list. Use ls ../.. for contents two levels above: Type the ls ~ command to list the contents in the users's home directory: Type the ls -d */ command to list only directories: Type the ls * command to list the contents of the directory with it's subdirectories: Type the ls -R command to list all files and directories with their corresponding subdirectories down to the last file: Type the ls -s command (the s is lowercase) to list files or directories with their sizes: Type the ls -l command to list the contents of the directory in a table format with columns including: Type the ls -lh command to list the files or directories in the same table format above, but with another column representing the size of each file/directory: Note that sizes are listed in bytes (B), megabytes (MB), gigabytes (GB), or terabytes (TB) when the file or directory's size is larger than 1024 bytes. Here is another example of the risks of mutation within a function: The list a that was passed as argument was mutated, even if that wasn't what you intended when you initially wrote the function. Tip: If the elements of the list are strings, they are sorted alphabetically. We can see that there are three elements with length 2: "BB", "AA", and "CC" in that order. ), but for now it's very important that you know that the sort()method modifies the list, so its original version is lost. Python list method reverse() reverses objects of list in place. 1. This is very important. The built-in range() method is especially used when using loops. You can make a tax-deductible donation here. 3) Adding element of list to a list. You can also add a -r flag to reverse the sorting order like so: ls -tr: Type the ls -S (the S is uppercase) command to list files or directories and sort by date or time in descending order (biggest to smallest). The ls command is used to list files or directories in Linux and other Unix-based operating systems. 1) Run ls without parameter. Tip: It is very important not to confuse the sort() method with the sorted() function, which is a function that works very similarly, but doesn't modify the original list. It is a part of the GNU core utilities package which is installed on all Linux distributions. You can use them to streamline everything from selecting and manipulating text to repeating commands you’ve already typed. List slicing is the method of splitting a subset of a list, and the indices of the list objects are also used for this. Now, notice that these three elements are in the same relative order in the final sorted list: This is because the algorithm is guaranteed to be stable and the three of them had the same intermediate value (key) during the sorting process (their length was 2, so their key was 2). The sort() method returns None – it does not return a sorted version of the list, like we might intuitively expect. With the sort() method, you can sort a list in either: This method is used to sort a list in place, which means that it mutates it or modifies it directly without creating additional copies, so remember: You will learn more about mutation in this article (I promise! This adds the element to the end of the list. When the 4 digits number is used, the first digit has the following meaning: setuid=4; setgid=2; sticky=1; no changes = 0 count () Returns the number of elements with the specified value. Using reverse () method The first option is python in-built reverse () method. And we’ve got the full list … Now that you know how to work with the reverse parameter, let's see the key parameter. Donations to freeCodeCamp go toward our education initiatives, and help pay for servers, services, and staff. Here we have a method call with these two arguments: Before explaining how they work, I would like to explain something that you probably noticed in the diagram above – in the method call, the names of the parameters have to be included before their corresponding values, like this: This is because they are keyword-only arguments. Tip: if we had used the default sorting process, all the strings that started with an uppercase letter would have come before all the strings that started with a lowercase letter: Here is an example using Object-Oriented Programming (OOP): If we have this very simple Python class: Then, if we define a function to get the age of these instances: We can sort the list based on their age by passing the get_age function an an argument: This is the final, sorted version of the list. We can pass the function len as the value of key, like this: Tip: Notice that we are only passing the name of the function (len) without parenthesis because we are not calling the function. Instead sorted() generates and returns a new copy of the list, already sorted. Launch your terminal and type ls to see this in action: The ls command also accepts some flags (also known as options) which are additional information that changes how files or directories are listed in your terminal. output Updated fruit list: ['orange', 'apple', 'banana', ['green apple', 'watermelon']] As you see when append green_fruit list to fruit list, it goes as a list not two element. If you are passing a custom value for them, their names have to be specified in the method call, followed by an equal sign = and their corresponding values, like this: Otherwise, if you try to pass the arguments directly as we normally do for positional parameters, you will see this error because the function will not know which argument corresponds to which parameter: Now that you know what keyword-only arguments are, let's start with reverse. In particular, the sort() method mutates the list. 2. How to sort a list in ascending and descending order. You will have to use exact name or id shown in the screenshot above to configure mouse or touchpad settings through the x… Using the reverse () method we can reverse the contents of the list object in-place i.e., we don’t need to create a new list instead we just copy the existing elements to the original list in reverse order. The ls command lists files and directories within the file system, and shows detailed information about them. We also have thousands of freeCodeCamp study groups around the world. These Multiple Choice Questions (mcq) should be practiced to improve the Python skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations. The first listed method is used. Ascending Order 2. This means we don’t need to create a new list to copy these elements to a new list but instead you can modify the original list. But you can take your skills to a whole new level by combining the effect of key and reverse in the same method call: These are the different combinations of the arguments and their effect: Since we are specifying the names of the arguments, we already know which value corresponds to which parameter, so we can include either key or reverse first in the list and the effect will be exactly the same. ) methods list are be compared directly list the content of the sort,! 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