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Adds a method for dynamically defining new struct types. This is helpful for situations where types aren't known until runtime, but you still want to provide type validation when encoding/decoding.
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One use of this is for dynamically defining a type used exclusively for extracting a few known fields from a larger structure. In code where the necessary fields are static, a classic struct definition would suffice. But for code where the fields aren't known until runtime, For example, here's a small script that parses and queries the current from operator import attrgetter
import msgspec
def top10_packages(sort_field):
# Dynamically define a new type with only the required fields
Package = msgspec.defstruct("Package", ["name", sort_field])
RepoData = msgspec.defstruct("RepoData", [("packages", dict[str, Package])])
# Load and parse the data into this new type
with open("current_repodata.json", "rb") as f:
repo_data = msgspec.json.decode(f.read(), type=RepoData)
# Sort by the designated field
packages = list(repo_data.packages.values())
getter = attrgetter(sort_field)
packages.sort(key=getter, reverse=True)
# Return the results
return [(p.name, getter(p)) for p in packages[:10]]
for name, size in top10_packages("size"):
print(f"- {name}: {size / (2 ** 20):.2f} MiB")Results: |
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Adds a method for dynamically defining new struct types. This is helpful
for situations where types aren't known until runtime, but you still
want to provide type validation when encoding/decoding.