single list query params convert just string

[lhs950204-eoding]

hi, i have some question.

i make request like this

# the api server must need list
params = {'a': [1], 'b': 2}
response = httpx.get(url, params=params)

and i predict query string like this

http://test.com?a=[1]&b=2
``

but result like this

http://test.com?a=1&b=2
``

this is bug...? or am i stupid...? please help

[ketpatil77]

This is expected. A Python list passed through params= becomes repeated query parameters:

str(httpx.QueryParams({"a": [1, 2], "b": 2}))
# 'a=1&a=2&b=2'

A one-element list therefore produces a=1. Query strings do not carry a Python/JSON list type by themselves. The server must interpret repeated values as a list, even when there is only one value.

If the API specifically requires the textual JSON value [1], serialize that value explicitly:

import json
response = httpx.get(url, params={"a": json.dumps([1]), "b": 2})
# a=%5B1%5D&b=2; the decoded value of a is '[1]'

If you control a FastAPI server and want repeated values, declare the field as a query list, for example a: Annotated[list[int], Query()].

Checked the repeated-key and JSON-string encodings on HTTPX 0.28.1. Which representation to use depends on the receiving API's contract.

HTTPX list parameter example.