To insert or append an empty element into a Python list you need to first define what is meant by the word empty. By empty do you mean an empty string, None or something else? While I may use None in this post you can easily substitute it for something else according to your requirements. To add an empty element into a list either replace the existing element with the empty variable or if inserting it at the end use the list method .append() or if inserting it at a specific place use the other list method .insert(). ...

Similar to the previous post on how to check if a string is empty the same principles and methods apply when checking if a list is empty in Python. To check if a list is empty either use the direct approach by using an expression where a list is compared to an empty list or use the boolean expression with a not operator (i.e. if not my_empty_list:) or use the built-in function len() to see if the length of the list is 0. ...

How can you check if a string is empty in Python? To determine if a string is empty in Python use of the following three means available: see if the string has any length by using the built-in len() function, do a direct comparison using the expression == "" or convert the string to a boolean data type and if the result is false it is an empty string. Let’s look at each approach and see how they perform. ...

A way to easily sort a list of strings equally is to change all the strings to lower case, but how do you change strings to lower case in Python? To change a string to lower case in Python use the string method .lower() like this: my_string.lower(). Similarly, to change a string to upper case in Python use the string method .upper() like this: my_string.upper(). An example of how this works is as follows: ...

It can be easy to sort a list, whether a list of strings or even a list of dictionaries, but can you sort a dictionary? One way to sort a dictionary by the values of each key : value pair in Python is to use a dictionary comprehension. Dictionary comprehensions are very similar to list comprehensions and have the following schema: 1 new_dict = { key: value for (key, value) in original_dict.items()} The first expression within the dictionary comprehension, the key: value portion, is the basic structure for setting any key and value pair within a dictionary. The second expression is familiar as the one-liner for loop, and within this statement we have a tuple representing the key and value returned from the dictionary’s .items() method. ...

What does the ord() function do? The built-in ord() function in Python converts any Unicode character into a number. It only takes one parameter which must be a single Unicode character, any more than one character produces an error. An example of the type of error you will get when sending more than 1 Unicode character is demonstrated here: 1 2 3 4 5 6 >>> ord('A') 65 >>> ord('ABC') Traceback (most recent call last): File "<input>", line 1, in <module> TypeError: ord() expected a character, but string of length 3 found Notice how Python informs us of what is expected – a character, but a string was passed in of length 3. ...

A common requirement in Python is to split a string into the characters which make up the string. I’ve previously shown how you can do this by breaking up a word into separate cells using a spreadsheet, but how do you do this in Python? As a string is a data type that can be iterated it means each unit element within the string, being a character, can be referencing an index on the string. ...

To find the length of a list use the built-in len() function which takes a single parameter that is iterable. For example this could be a string, list, tuple or dictionary and here is how it would look: 1 2 3 4 5 6 7 8 9 >>> my_list = ['a', 'b', 'c'] >>> len(my_list) 3 >>> my_dict = {'a': 100, 'b': 200, 'c': 300} >>> len(my_dict) 3 >>> my_str = 'How long is a piece of string?' >>> len(my_str) 30 This may be the easiest and quickest way of being able to find the length of a list and other data types, but what if you want to exclude certain items from your list? ...

One way to determine if one value does not equal another is to use the != comparator, but what if you’re not comparing two values – how can you determine if something is not true? Python has an inbuilt operator aptly called not which permits a user to check a variable, or a function’s result to test if the variable or returned value is not valid. Some classic use cases of this type of logic applied in my Python code have been checking if a file exists, other instances have been when scraping a web page and checking if the element existed on the page. ...

Previously I looked at how to use the enumerate() built-in function with a for loop to provide two variables when iterating through a list. In that article the enumerate() function provides both an index number and the element in each list by wrapping these together into a tuple. But what happens when the enumerate() function is applied to a dictionary? As done previously let’s inspect the output of the enumerated dictionary by printing its contents: ...