How to encode URLs in Dart?

Use Dart Uri Class

var uri = 'http://example.com/path/to/page?name=ferret john';
var encoded = Uri.encodeFull(uri);
assert(encoded == 'http://example.com/path/to/page?name=ferret%20john');

var decoded = Uri.decodeFull(encoded);
assert(uri == decoded);

You are doing too much. In this case, you only need to do: parsedData = Uri.encodeComponent(STR_DATA); to get the same result as the Python code.