Lists, tuples, dict, sets, ...

cats.png

Python has several sequential types that look like lists of things, like the collection of cats above. In the last section, we assigned a single value to a variable name. Here, what if you need to store a long list of information, which doesn't change over time? Say, for example, the names of the months of the year. Or maybe a long list of information, that does change over time? Say, for example, the names of all your cats. You might get new cats! What about a phone book? For that you need to do a bit of referencing - you would have a list of names, and attached to each of those names, a phone number. How would you do that?

  • Lists are what they seem - a list of values. Each one of them is numbered, starting from zero - the first one is numbered zero, the second 1, the third 2, etc. You can remove values from the list, and add new values to the end. Example: Your many cats' names.
  • Tuples are just like lists, but you can't change their values. The values that you give it first up, are the values that you are stuck with for the rest of the program. Again, each value is numbered starting from zero, for easy reference. Example: the names of the months of the year.
  • Dictionaries are similar to what their name suggests - a dictionary. In a dictionary, you have an 'index' of words, and for each of them a definition. In python, the word is called a 'key', and the definition a 'value'. The values in a dictionary aren't numbered - tare similar to what their name suggests - a dictionary. In a dictionary, you have an 'index' of words, and for each of them a definition. In python, the word is called a 'key', and the definition a 'value'. The values in a dictionary aren't numbered - they aren't in any specific order, either - the key does the same thing. You can add, remove, and modify the values in dictionaries. Example: telephone book.
  • Sets are lists with no duplicate entries. Let's say you want to collect a list of words used in a paragraph. A set contains an unordered collection of unique and immutable objects. The set data type is, as the name implies, Python implementation of the sets as they are known from mathematics. This explains, why sets unlike lists or tuples can't have multiple occurrences of the same element.