If I had to keep only one Python data structure, I would keep the dictionary. Lists are useful, sets are useful, but dictionaries are the tool I reach for most often in real work, because so much of programming is really about looking something up by name.<\/p>\n\n
A dictionary is a set of pairs: a key and the value that goes with it. That simple shape turns out to be remarkably flexible. I use it for configuration, where a setting name maps to its value. I use it for counting, where a word or an event maps to how many times I have seen it. I use it for grouping, where a category maps to a list of items in that category. The structure stays the same, even as the job changes.<\/p>\n\n
Configuration is the clearest example. A small script often starts with a few variables scattered through the code, and then grows. Moving those values into a dictionary, with clear names as keys, makes the script easier to read and easier to change. When a setting needs to change, I change it in one place, and the rest of the code reads it from there.<\/p>\n\n
Counting is another place where dictionaries quietly do the work. Instead of keeping parallel lists of items and counts, and trying to keep them in sync, I let the item be the key and the count be the value. Each time I see the item, I increase its count. The code is short, the intent is obvious, and there is no second list to fall out of step.<\/p>\n\n
Grouping follows the same pattern. If I need to collect log lines by service, or files by type, or tasks by status, a dictionary with a list under each key does the job. I do not need a special data structure for each case. I need the same one, used well.<\/p>\n\n
Dictionaries also make JSON feel natural, because JSON objects and Python dictionaries map closely to each other. When I read data from a web service or a file, it often arrives in a shape I can work with immediately, using names I already understand. That closeness removes a whole layer of translation that used to slow me down in other languages.<\/p>\n\n
There are limits, of course. Keys need to be unique, so a dictionary is a poor choice when I genuinely need duplicates in order. And a dictionary with unclear keys is worse than no dictionary at all. I try to choose key names that explain themselves, because the next person reading the code, who is often future me, should not have to guess what a key means.<\/p>\n\n
The practical takeaway is to start with a dictionary when the problem is really a lookup. Ask what the name is, and what belongs under that name. If you can answer those two questions, you probably have a dictionary-shaped problem, and you probably do not need anything more complicated to solve it well.<\/p>\n\n
One small example stays with me: a script that read a messy list of records and needed a quick summary. Instead of building a class or a database for a one-off job, I grouped the records by a single field in a dictionary and printed the totals. The script stayed short, the result was easy to check, and I threw nothing away that I needed later.<\/p>","protected":false},"excerpt":{"rendered":"
If I had to keep only one Python data structure, I would keep the dictionary. Lists are useful, sets are useful, but dictionaries are the tool I reach for most often in real work, because so much of programming is really about looking something up by name. A dictionary is a set of pairs: a […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-46","post","type-post","status-publish","format-standard","hentry","category-technical-commentary"],"_links":{"self":[{"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/posts\/46","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/comments?post=46"}],"version-history":[{"count":1,"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/posts\/46\/revisions"}],"predecessor-version":[{"id":47,"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/posts\/46\/revisions\/47"}],"wp:attachment":[{"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/media?parent=46"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/categories?post=46"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/quentinpidcock.com\/content\/wp-json\/wp\/v2\/tags?post=46"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}