Tips & Tricks¶

Below are some nice things to know as you're getting started.

pathlib¶

pathlib is a module built in to Python 3.4+ that makes working with filepaths easier.

Without something like pathlib, it can be tempting to create file path strings using string concatenation, like this:

dst_path = "/path/to/dst/"

year_path = "/path/to/dst/2014/median.tif"

While this works well enough, creating new variables from scratch for many file increases the risk of spelling errors, makes paths difficult to edit en masse, and requires repeating yourself over and over.

Here is an example of pathlib accomplishing the same thing:

from pathlib import Path

dst_dir = Path(/path/to/dst)

# you can use slashes to combine parts of a path together
# now year_dir is a Path object pointing to /path/to/dst/2014/median.tif
year_path = dst_dir / "2014" / "median.tif"

# you can use Path.as_posix() to get a string from the path
assert isinstance(year_path.as_posix(), str)

Here, if someone were to edit dst_dir on the third line to point somewhere else, it would automatically update year_path and any other paths that reference it. Another nifty feature is that Path objects provide functions for quick analysis:

from pathlib import Path

example_path = Path("/path/to/dst/hello_world.txt")

example_path.parent # (1)!
example_path.exists() # (2)!
example_path.name # (3)!
example_path.stem # (4)!

This attribute is also a Path object, pointing to the /path/to/dst directory.
This returns a boolean representing whether or not this path actually exists on your filesystem.
This returns the string "hello_world.txt"
This returns the string "hello_world"

To see a full list of pathlib features, checkout out its documentation here.

The Python Debugger¶

An underappreciated feature of Python is the Python Debugger, a tool that allows you to stop execution of a Python program wherever you like and inspect it line-by-line. It can be invoked by inserting breakpoint() anywhere in your script, like this:

str_var = "Hello, World!"
breakpoint()

When executing this code block, Python will set the str_var variable and then stop execution, dropping you into an interactive debugging tool. There are many commands you can use in this tool, or if you enter valid Python code it will execute normally. The interact command will switch you to a normal Python interpreter, preserving variables and other elements from the current scope.