Python Discoveries

Here, whenever I will remember, I will be writing what I have discovered about Python when creating one project or the other.

Functionalities that took me a long time to discover and when I finally did - it helped me a lot.

First of all I don't want to forget about these functions, second of all - I would like to share them with you.

1 Scope

You can assign a returned value from functions to a variable

I was returning a value from function, wanted to use it another function. I had to assign the returned value to a function first and only then I could use it. SCOPE is the important word here.

Thanks to Karina

2 f"" string > templates

Qrcode pkc

I had to recreate a QR code template that is created with batch to a program in python(more controls, better gui, etc).

So I have chosen something like this for this task. Had a massive template with certain strings that had to be replaced. All is good, managed to make it work, but whenever I would have a: 9999$A99999 my delimiter and value that $A surrounded with other symbols - the delimiter would not be replaced with what I have described.

f"99999{A}99999" has no problem doing that, this is why I have chosen it for this project.

3 flask dispachermiddleware

Module and imports. Running multiple flask apps

For this project here.

even though the data.py is in basically the same location as main.py - I still had to import all the modules from root.. from II.web_app.data import data. This was strange.

4 Python set()

The set() function creates a set. No repeating values.

list_numbers = [1,2,3,4,2,5,5,1]

# create set from list
numbers_set = set(list_numbers)

print(numbers_set)

Useful when I wanted to extract all authors in a list ONCE.

Amazing, thanks to Karina.

5 listdir vs chdir

This one confused me. I ran a for loop similar to this:

x = ./Dropbox
dir = os.listdir(x)
print(dir)

for file in dir:
    # do this and that

and I kept wondering why my for loops runs IN THE directory where this script is placed(I printed it out, it knows the dir I want) and not in the directory that I specified in x.

Now it seems obvious, but I simply should have changed the director to the specified one before running the for loop.

something similar to this:

for file in os.listdir(os.chdir(x)):