Python

Socratica Python Programming Tutorials (Computer Science) - YouTube

Basics

Use dir() to look up what we can use on an object like this:

example = set()
dir(example)
#[... '_and_', '_class_', '_contains_', '_delattr_', '_dir_', '_doc_' ...  'issuperset', 'pop', 'remove', 'symmetric_difference', 'symmetric_difference_update', 'union', 'update'...]

Some data classes

• Lists - stores duplicates, mutable.
  • Also, collections.deque similar to a list but optimized for adding/removing from both ends.

  my_list = [1, 2, 2, 3]
  print(my_list)  # Output: [1, 2, 2, 3]

• Sets - don’t store duplicates, no order, mutable.
  • Also, frozenset add immutability my_frozenset = frozenset([1, 2, 2, 3])

	my_set = {1, 2, 2, 3}
	print(my_set)  # Output: {1, 2, 3}

• Tuples - stores duplicates, immutable
  • Also, collections.namedtuple - Like a tuple, but with named fields for better readability Point = namedtuple("Point", ["x", "y"])

	my_tuple = (1, 2, 2, 3)
	print(my_tuple)  # Output: (1, 2, 2, 3)

• Dictionaries - stores duplicates, mutable, key/value.
  • Also, collections.defaultdict - provides a default value for missing keys.

	my_dict = {"a": 1, "b": 2, "a": 3}
	print(my_dict)  # Output: {'a': 3, 'b': 2}

Variable scopes

When a variable is encountered, Python searches for it in the following order of scopes (LEGB):

• Local: defined within a function
  • 
• Enclosing: function inside a function.
  • 
• Global: outside of function or defined by keyword global
  • 
• Built-in: which contains all keywords, functions, exceptions and attributes, which are built-in.
  

Text and number formatting

x = float(input("what is x")) # 999
y = float(input("what is y")) # 1
z = round(x+y)
print(f"{z:,}") # Outputs: 1,000 formatted number
 
x = 2
y = 3
z = (x / y)
print(f"{z:.f2}") # Outputs: 0.67 formatted number

List comprehension vs generator expression

#The expression
domain.lower() in repo_field for domain in domains
#without square brackets is a **generator expression**. A list comprehension would include square brackets, like:
[domain.lower() in repo_field for domain in domains]
#So while they look similar, the one without the brackets is lazy and produces a generator rather than a full list.

Fibonacci Sequence in Python

Fibonacci sequence is a sequence in which each element is the sum of the two elements that precede it, starting from 0 and 1: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ...

Package management

pip (barebones)

What is Python’s site-packages directory? - Stack Overflow
python - What does pip install . (dot) mean? - Stack Overflow

UV (better than pip and else)

Combines package management, environment management and locking via uv lock and uv sync --lock

Lock file, what?

Tl;dr: uv sync would sync with pyproject.toml to install packages and create/relock uv.lock file. While uv sync --lock would make sure that if new package update/tree changed in pip repo it would preserve existing state, not installing updates.

UV has ability to record all package dependencies and versions into a lock file, making deployments consistent. For example, you developed locally and now pushing container image, you can instruct UV in docker file to import uv.lock too so that it’s identical.

What is no-install-project?:

`uv sync --no-install-project`

The uv tool will do the following:

• Reads your pyproject.toml (specifically the [project.dependencies] section)
• Installs those dependencies directly using its own resolver and downloader, without calling pip install .
• It uses uv’s native Rust-based backend, which is faster and lower-level than pip

Linting and code checker

Ruff