Today was fun. Worked through some challenging exercises. Had a bug that took me a minute to figure out: forgot to add a return statement on a function. Macrodata Refinement is hard :)

Some things covered:

File management - prefereed way to open different file types using with

Functions

• how to call function interactively e.g. python3 -i pcost.py
• sys.argv is a list that contains passed arguments on the command line (if any).

Datatypes and Data structures

• list(d) - returns all the keys.
• d.keys() returns a special dict_keys object which is an overlay on the original dictionary that always gives you the current keys—even if the dictionary changes.
• with a list of tuple pairs called items, you can create a dictionary dict(items)

Containers

• Lists. use when the order of the data matters and mostly containing the same data type.
• Dictionaries. useful if you want fast random lookups (by key name). Before Python 3.7, dictionaries did not preserve insertion order. d.get(key, default) for look up where a key might not exist.
• Sets. Unordered collection of unique items. useful for duplicate elimination.

Tomorrow: work through sections 2.3 to 2.6