Python Basics Exercises: Strings and String Methods (Overview)

Given three variables:

string1 = "Animals"
string2 = "Badger"
string3 = "Honey Bee"

the only way I found to put the values in a list is this:

values_list = [globals()[f'string{i}'] for i in range(1,4)]

Is it good practice to use globals() like that ? If not, how to achieve what I’m trying to do?

Thanks

@emru67 Generally, it’s not considered a good practice to use globals() in Python. One reason for that is it introduces a dependency on your variable names. So, if you change those names at some point, you’ll break the code without noticing until you actually run the program and see a runtime error.

Can you describe what you’re trying to achieve on a higher level? There might be a more elegant way to approach your problem.

@emru67 if you just want to put the values into a list, then you can do this:

string1 = "Animals"
string2 = "Badger"
string3 = "Honey Bee"

values_list = [string1, string2, string3]

But you might be after something else? You’ll learn more about lists in a later course in this learning path.

Thanks for the prompt answers. What I’m trying to understand is how to go through any variables present in a script without knowing their names in advance and without having to hard code them by hand. It’s just something I don’t feel I grasped fully. Originally the question raised because I imagined a scenario where the variables names are system produced, there may be two or twenty (es.: string1, string2, string(n)…). The solution I found doesn’t feel correct, but I couldn’t think of anything else. I already completed the List course, that’s why I know about list comprehensions. I apologize for not making my point clearer. Thanks

@emru67 Can you clarify this part, please?

I imagined a scenario where the variables names are system produced,

I can’t think of a real-life use case for this. Data produced by some kind of system should be separate from the source code that processes it. Typically, you’d load the data from a file, a database, or a web service rather than manipulate the individual variables unless you had a good reason to perform code introspection.

You are right, I cannot think of a real life scenario as well…

What happened was that I wanted to make the excercise I was doing more interesting using a loop to apply all the various string methods to the variables values (.lower(), .upper(), etc.). When I tried I found out that I couldn’t easily access the variables except for hard coding them by hand. Then it became a challenge to find a way to get to them programmatically…I learned a few things along the way which is the goal anyway…

Thanks all for your support

@emru67 if you wanted to see the names that you defined in your current script or session, then you could use the globals() function and e.g. a list comprehension to see them all:

>>> string1 = "hi!"
>>> string2 = "ho!"
>>> user_defined_names = [s for s in globals() if not s.startswith("_")]
>>> user_defined_names
['string1', 'string2']

Here, you’re using a list comprehension to filter out all names that start with a single or double underscore to remove the built-in non-public names and show only the ones you defined. Assuming that you didn’t define any names with a leading underscore, that is ;P

Then, you could theoretically use that information to look them up in the globals dictionary and apply string methods on all of them programmatically:

>>> for name in user_defined_names:
...     globals()[name].upper()
...
'HI!'
'HO!'

However, this isn’t a good idea. Python allows you to do many things, but if it’s hacky to get there, then you can assume that there’s probably a reason for that. Also, doing something like that is going into Python’s internals, which is potentially a bit early when you’re working through the Python Basics course.

But on the other hand, everyone learns differently, and if this is exciting to you then I’d encourage you to keep exploring behind the scenes :))

Thanks again for the support and the clear explanation. I do like to explore and I’m a bit more “advanced” then basic string manipulation, that was a review of things done. It’s important to understand the inner workings of a language to really know what’s going on. At Real Python you always encourage experimenting to gain knowledge and it’s one of the reasons why I joined.

Thanks all for your help

Yay, of course, happy to @emru67! Good idea to revisit basic concepts and dive deeper 🙌

After completing strings and string method chapter i had made the calculator. (:,)