Python Files¶
Once you have chosen a text-editor, you are ready to begin writing Python files.
Python file structure¶
What does a typical Python file look like?
# Import standard lib libraries
import requests
# Import external libraries
import numpy as np
import pandas
# Import internal libraries
def my_function(x, y):
return x + y
def another_function(x, y):
return x*y
# If we want to do particular things when the file is run, we
# put it in the block below
if __name__ == "__main__":
print(my_function(2, 2))
print(another_function(2, 2))
A slightly more useful file might be something like the following:
import pandas as pd
def convert_to_TX_time(ts):
return ts.tz_convert("US/Central")
def convert_to_DE_time(ts):
return ts.tz_convert("Europe/Berlin")
if __name__ == "__main__":
ts = pd.Timestamp.utcnow()
print(f"The time in TX is {convert_to_TX_time(ts)}")
print(f"The time in DE is {convert_to_DE_time(ts)}")
Running a Python file¶
Once we’ve written and saved a Python file, we can run it using python filename.py
When we run the file, it will by default execute all of the code in the file. We can specify that it should do a particular subset of things using the if statement we’ve included at the bottom of our files.
Building internal libraries¶
As you work on slightly more involved projects, you will often (or at least you should) build a small collection of helper functions and components to minimize the amount of repetition in your code.
How can we package this up in a way that allows it to be usable? We can create our own package within our project folder!
File structure¶
Imagine we have a file structure that has the following form
- web_scraping_project
- scrapers
- __init__.py
- scraper1.py
- scraper2.py
- helpers
- __init__.py
- helper_functions.py
- other_stuff.py
The __init__.py file under the scrapers and helpers folders denotes that these two folders should be interpreted as Python packages. This means that we could import code from them just like we are able to import code from numpy or pandas.
We will see an example of doing this in the web scraping section