alt.Color fails mypy --strict with error: Call to untyped function "Color" in typed context [no-untyped-call]

[wyattscarpenter]

What happened?

I use altair in my project, which is typedchecked with mypy strict mode. When I have a graph in that project which uses alt.Color, I get error: Call to untyped function "Color" in typed context [no-untyped-call] from mypy --strict. Oddly, this does not happen to other alt.Whatever objects, only color. I can't be sure if this is an altair bug or a mypy bug, to be honest.

Here's a minimal example:

import altair as alt
import pandas as pd
dicted_rows = {"a": [1, 2, 3], "b": [4, 5, 6], "c": ["red", "blue", "yellow"]}
chart = alt.Chart(pd.DataFrame(dicted_rows)).mark_circle(size=90).encode(alt.X("a"), alt.Y("b"), alt.Color("c"))
chart.save('chart.html') #note: this works fine

Results from mypy version 1.9.0 (compiled: yes):

$ mypy "minimal altair example.py"
Success: no issues found in 1 source file

$ mypy --strict "minimal altair example.py"
minimal altair example.py:4: error: Call to untyped function "Color" in typed context  [no-untyped-call]
Found 1 error in 1 file (checked 1 source file)

What would you like to happen instead?

The types should be annotated appropriately so Color is deduced to be a typed function and therefore mypy strict would not report an error.

I'm not sure exactly what this would involve. https://peps.python.org/pep-0484/ says the return type of init ought to be None, so that's somewhere to start, maybe, perhaps.

Which version of Altair are you using?

5.3.0

[binste]

Weird, Color is type annotated in the same way as other encoding channels such as X and Y. Maybe mypy somehow gets confused... Thanks for raising it! I'll have a look.

[wyattscarpenter]

It also seems to fail pyright, erroring for all three arguments.

In case it helps, here's the output from various type checkers, using reveal_type on alt.X, alt.Y, and alt.Color, and some other parts as well:

import altair as alt
import pandas as pd
dicted_rows = {"a": [1, 2, 3], "b": [4, 5, 6], "c": ["red", "blue", "yellow"]}
chart = alt.Chart(pd.DataFrame(dicted_rows)).mark_circle(size=90).encode(alt.X("a"), alt.Y("b"), alt.Color("c"))
chart.save('chart.html') #note: this works fine
reveal_type(alt.X)
reveal_type(alt.Y)
reveal_type(alt.Color)
reveal_type(alt.Chart)
reveal_type(alt.Chart(pd.DataFrame(dicted_rows)).mark_circle(size=90))
reveal_type(alt.Chart(pd.DataFrame(dicted_rows)).mark_circle(size=90).encode)

pyright 1.1.360:

c:\experiment\minalt.py
  c:\experiment\minalt.py:4:74 - error: Argument of type "X" cannot be assigned to parameter "angle" of type "str | Angle | dict[Unknown, Unknown] | AngleDatum | AngleValue | UndefinedType"
    Type "X" is incompatible with type "str | Angle | dict[Unknown, Unknown] | AngleDatum | AngleValue | UndefinedType"
      "X" is incompatible with "str"
      "X" is incompatible with "Angle"
      "X" is incompatible with "dict[Unknown, Unknown]"
      "X" is incompatible with "AngleDatum"
      "X" is incompatible with "AngleValue"
      "X" is incompatible with "UndefinedType" (reportArgumentType)
  c:\experiment\minalt.py:4:86 - error: Argument of type "Y" cannot be assigned to parameter "color" of type "str | Color | dict[Unknown, Unknown] | ColorDatum | ColorValue | UndefinedType"
    Type "Y" is incompatible with type "str | Color | dict[Unknown, Unknown] | ColorDatum | ColorValue | UndefinedType"
      "Y" is incompatible with "str"
      "Y" is incompatible with "Color"
      "Y" is incompatible with "dict[Unknown, Unknown]"
      "Y" is incompatible with "ColorDatum"
      "Y" is incompatible with "ColorValue"
      "Y" is incompatible with "UndefinedType" (reportArgumentType)
  c:\experiment\minalt.py:4:98 - error: Argument of type "Color" cannot be assigned to parameter "column" of type "str | Column | dict[Unknown, Unknown] | UndefinedType"
    Type "Color" is incompatible with type "str | Column | dict[Unknown, Unknown] | UndefinedType"
      "Color" is incompatible with "str"
      "Color" is incompatible with "Column"
      "Color" is incompatible with "dict[Unknown, Unknown]"
      "Color" is incompatible with "UndefinedType" (reportArgumentType)
  c:\experiment\minalt.py:6:13 - information: Type of "alt.X" is "type[X]"
  c:\experiment\minalt.py:7:13 - information: Type of "alt.Y" is "type[Y]"
  c:\experiment\minalt.py:8:13 - information: Type of "alt.Color" is "type[Color]"
  c:\experiment\minalt.py:9:13 - information: Type of "alt.Chart" is "type[Chart]"
  c:\experiment\minalt.py:10:13 - information: Type of "alt.Chart(pd.DataFrame(dicted_rows)).mark_circle(size=90)" is "Chart"
  c:\experiment\minalt.py:11:13 - information: Type of "alt.Chart(pd.DataFrame(dicted_rows)).mark_circle(size=90).encode" is "(angle: str | Angle | dict[Unknown, Unknown] | AngleDatum | AngleValue | UndefinedType = Undefined, color: str | Color | dict[Unknown, Unknown] | ColorDatum | ColorValue | UndefinedType = Undefined, column: str | Column | dict[Unknown, Unknown] | UndefinedType = Undefined, description: str | Description | dict[Unknown, Unknown] | DescriptionValue | UndefinedType = Undefined, detail: str | Detail | dict[Unknown, Unknown] | list[Unknown] | UndefinedType = Undefined, facet: str | Facet | dict[Unknown, Unknown] | UndefinedType = Undefined, fill: str | Fill | dict[Unknown, Unknown] | FillDatum | FillValue | UndefinedType = Undefined, fillOpacity: str | FillOpacity | dict[Unknown, Unknown] | FillOpacityDatum | FillOpacityValue | UndefinedType = Undefined, href: str | Href | dict[Unknown, Unknown] | HrefValue | UndefinedType = Undefined, key: str | Key | dict[Unknown, Unknown] | UndefinedType = Undefined, latitude: str | Latitude | dict[Unknown, Unknown] | LatitudeDatum | UndefinedType = Undefined, latitude2: str | Latitude2 | dict[Unknown, Unknown] | Latitude2Datum | Latitude2Value | UndefinedType = Undefined, longitude: str | Longitude | dict[Unknown, Unknown] | LongitudeDatum | UndefinedType = Undefined, longitude2: str | Longitude2 | dict[Unknown, Unknown] | Longitude2Datum | Longitude2Value | UndefinedType = Undefined, opacity: str | Opacity | dict[Unknown, Unknown] | OpacityDatum | OpacityValue | UndefinedType = Undefined, order: str | Order | dict[Unknown, Unknown] | list[Unknown] | OrderValue | UndefinedType = Undefined, radius: str | Radius | dict[Unknown, Unknown] | RadiusDatum | RadiusValue | UndefinedType = Undefined, radius2: str | Radius2 | dict[Unknown, Unknown] | Radius2Datum | Radius2Value | UndefinedType = Undefined, row: str | Row | dict[Unknown, Unknown] | UndefinedType = Undefined, shape: str | Shape | dict[Unknown, Unknown] | ShapeDatum | ShapeValue | UndefinedType = Undefined, size: str | Size | dict[Unknown, Unknown] | SizeDatum | SizeValue | UndefinedType = Undefined, stroke: str | Stroke | dict[Unknown, Unknown] | StrokeDatum | StrokeValue | UndefinedType = Undefined, strokeDash: str | StrokeDash | dict[Unknown, Unknown] | StrokeDashDatum | StrokeDashValue | UndefinedType = Undefined, strokeOpacity: str | StrokeOpacity | dict[Unknown, Unknown] | StrokeOpacityDatum | StrokeOpacityValue | UndefinedType = Undefined, strokeWidth: str | StrokeWidth | dict[Unknown, Unknown] | StrokeWidthDatum | StrokeWidthValue | UndefinedType = Undefined, text: str | Text | dict[Unknown, Unknown] | TextDatum | TextValue | UndefinedType = Undefined, theta: str | Theta | dict[Unknown, Unknown] | ThetaDatum | ThetaValue | UndefinedType = Undefined, theta2: str | Theta2 | dict[Unknown, Unknown] | Theta2Datum | Theta2Value | UndefinedType = Undefined, tooltip: str | Tooltip | dict[Unknown, Unknown] | list[Unknown] | TooltipValue | UndefinedType = Undefined, url: str | Url | dict[Unknown, Unknown] | UrlValue | UndefinedType = Undefined, x: str | X | dict[Unknown, Unknown] | XDatum | XValue | UndefinedType = Undefined, x2: str | X2 | dict[Unknown, Unknown] | X2Datum | X2Value | UndefinedType = Undefined, xError: str | XError | dict[Unknown, Unknown] | XErrorValue | UndefinedType = Undefined, xError2: str | XError2 | dict[Unknown, Unknown] | XError2Value | UndefinedType = Undefined, xOffset: str | XOffset | dict[Unknown, Unknown] | XOffsetDatum | XOffsetValue | UndefinedType = Undefined, y: str | Y | dict[Unknown, Unknown] | YDatum | YValue | UndefinedType = Undefined, y2: str | Y2 | dict[Unknown, Unknown] | Y2Datum | Y2Value | UndefinedType = Undefined, yError: str | YError | dict[Unknown, Unknown] | YErrorValue | UndefinedType = Undefined, yError2: str | YError2 | dict[Unknown, Unknown] | YError2Value | UndefinedType = Undefined, yOffset: str | YOffset | dict[Unknown, Unknown] | YOffsetDatum | YOffsetValue | UndefinedType = Undefined) -> Chart"
3 errors, 0 warnings, 6 informations

mypy 1.9.0 (compiled: yes), with --strict:

minalt.py:4: error: Call to untyped function "Color" in typed context  [no-untyped-call]
minalt.py:6: note: Revealed type is "def (shorthand: Union[builtins.str, builtins.dict[Any, Any], typing.Sequence[builtins.str], Any, altair.utils.schemapi.UndefinedType] =, aggregate: Union[builtins.dict[Any, Any], Any, Literal['average'], Literal['count'], Literal['distinct'], Literal['max'], Literal['mean'], Literal['median'], Literal['min'], Literal['missing'], Literal['product'], Literal['q1'], Literal['q3'], Literal['ci0'], Literal['ci1'], Literal['stderr'], Literal['stdev'], Literal['stdevp'], Literal['sum'], Literal['valid'], Literal['values'], Literal['variance'], Literal['variancep'], Literal['exponential'], Literal['exponentialb'], altair.utils.schemapi.UndefinedType] =, axis: Union[builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, bandPosition: Union[builtins.float, altair.utils.schemapi.UndefinedType] =, bin: Union[builtins.str, builtins.bool, builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, field: Union[builtins.str, builtins.dict[Any, Any], Any, altair.utils.schemapi.UndefinedType] =, impute: Union[builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, scale: Union[builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, sort: Union[builtins.dict[Any, Any], None, typing.Sequence[builtins.str], typing.Sequence[builtins.bool], Any, typing.Sequence[builtins.float], Literal['ascending'], Literal['descending'], typing.Sequence[Union[builtins.dict[Any, Any], Any]], Literal['x'], Literal['y'], Literal['color'], Literal['fill'], Literal['stroke'], Literal['strokeWidth'], Literal['size'], Literal['shape'], Literal['fillOpacity'], Literal['strokeOpacity'], Literal['opacity'], Literal['text'], Literal['-x'], Literal['-y'], Literal['-color'], Literal['-fill'], Literal['-stroke'], Literal['-strokeWidth'], Literal['-size'], Literal['-shape'], Literal['-fillOpacity'], Literal['-strokeOpacity'], Literal['-opacity'], Literal['-text'], altair.utils.schemapi.UndefinedType] =, stack: Union[builtins.bool, None, Any, Literal['zero'], Literal['center'], Literal['normalize'], altair.utils.schemapi.UndefinedType] =, timeUnit: Union[builtins.dict[Any, Any], Any, Literal['year'], Literal['quarter'], Literal['month'], Literal['week'], Literal['day'], Literal['dayofyear'], Literal['date'], Literal['hours'], Literal['minutes'], Literal['seconds'], Literal['milliseconds'], Literal['utcyear'], Literal['utcquarter'], Literal['utcmonth'], Literal['utcweek'], Literal['utcday'], Literal['utcdayofyear'], Literal['utcdate'], Literal['utchours'], Literal['utcminutes'], Literal['utcseconds'], Literal['utcmilliseconds'], Literal['binnedyear'], Literal['binnedyearquarter'], Literal['binnedyearquartermonth'], Literal['binnedyearmonth'], Literal['binnedyearmonthdate'], Literal['binnedyearmonthdatehours'], Literal['binnedyearmonthdatehoursminutes'], Literal['binnedyearmonthdatehoursminutesseconds'], Literal['binnedyearweek'], Literal['binnedyearweekday'], Literal['binnedyearweekdayhours'], Literal['binnedyearweekdayhoursminutes'], Literal['binnedyearweekdayhoursminutesseconds'], Literal['binnedyeardayofyear'], Literal['binnedutcyear'], Literal['binnedutcyearquarter'], Literal['binnedutcyearquartermonth'], Literal['binnedutcyearmonth'], Literal['binnedutcyearmonthdate'], Literal['binnedutcyearmonthdatehours'], Literal['binnedutcyearmonthdatehoursminutes'], Literal['binnedutcyearmonthdatehoursminutesseconds'], Literal['binnedutcyearweek'], Literal['binnedutcyearweekday'], Literal['binnedutcyearweekdayhours'], Literal['binnedutcyearweekdayhoursminutes'], Literal['binnedutcyearweekdayhoursminutesseconds'], Literal['binnedutcyeardayofyear'], Literal['yearquarter'], Literal['yearquartermonth'], Literal['yearmonth'], Literal['yearmonthdate'], Literal['yearmonthdatehours'], Literal['yearmonthdatehoursminutes'], Literal['yearmonthdatehoursminutesseconds'], Literal['yearweek'], Literal['yearweekday'], Literal['yearweekdayhours'], Literal['yearweekdayhoursminutes'], Literal['yearweekdayhoursminutesseconds'], Literal['yeardayofyear'], Literal['quartermonth'], Literal['monthdate'], Literal['monthdatehours'], Literal['monthdatehoursminutes'], Literal['monthdatehoursminutesseconds'], Literal['weekday'], Literal['weekdayhours'], Literal['weekdayhoursminutes'], Literal['weekdayhoursminutesseconds'], Literal['dayhours'], Literal['dayhoursminutes'], Literal['dayhoursminutesseconds'], Literal['hoursminutes'], Literal['hoursminutesseconds'], Literal['minutesseconds'], Literal['secondsmilliseconds'], Literal['utcyearquarter'], Literal['utcyearquartermonth'], Literal['utcyearmonth'], Literal['utcyearmonthdate'], Literal['utcyearmonthdatehours'], Literal['utcyearmonthdatehoursminutes'], Literal['utcyearmonthdatehoursminutesseconds'], Literal['utcyearweek'], Literal['utcyearweekday'], Literal['utcyearweekdayhours'], Literal['utcyearweekdayhoursminutes'], Literal['utcyearweekdayhoursminutesseconds'], Literal['utcyeardayofyear'], Literal['utcquartermonth'], Literal['utcmonthdate'], Literal['utcmonthdatehours'], Literal['utcmonthdatehoursminutes'], Literal['utcmonthdatehoursminutesseconds'], Literal['utcweekday'], Literal['utcweeksdayhours'], Literal['utcweekdayhoursminutes'], Literal['utcweekdayhoursminutesseconds'], Literal['utcdayhours'], Literal['utcdayhoursminutes'], Literal['utcdayhoursminutesseconds'], Literal['utchoursminutes'], Literal['utchoursminutesseconds'], Literal['utcminutesseconds'], Literal['utcsecondsmilliseconds'], altair.utils.schemapi.UndefinedType] =, title: Union[builtins.str, None, typing.Sequence[builtins.str], Any, altair.utils.schemapi.UndefinedType] =, type: Union[Any, Literal['quantitative'], Literal['ordinal'], Literal['temporal'], Literal['nominal'], altair.utils.schemapi.UndefinedType] =, **kwds: Any) -> altair.vegalite.v5.schema.channels.X"
minalt.py:7: note: Revealed type is "def (shorthand: Union[builtins.str, builtins.dict[Any, Any], typing.Sequence[builtins.str], Any, altair.utils.schemapi.UndefinedType] =, aggregate: Union[builtins.dict[Any, Any], Any, Literal['average'], Literal['count'], Literal['distinct'], Literal['max'], Literal['mean'], Literal['median'], Literal['min'], Literal['missing'], Literal['product'], Literal['q1'], Literal['q3'], Literal['ci0'], Literal['ci1'], Literal['stderr'], Literal['stdev'], Literal['stdevp'], Literal['sum'], Literal['valid'], Literal['values'], Literal['variance'], Literal['variancep'], Literal['exponential'], Literal['exponentialb'], altair.utils.schemapi.UndefinedType] =, axis: Union[builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, bandPosition: Union[builtins.float, altair.utils.schemapi.UndefinedType] =, bin: Union[builtins.str, builtins.bool, builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, field: Union[builtins.str, builtins.dict[Any, Any], Any, altair.utils.schemapi.UndefinedType] =, impute: Union[builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, scale: Union[builtins.dict[Any, Any], None, Any, altair.utils.schemapi.UndefinedType] =, sort: Union[builtins.dict[Any, Any], None, typing.Sequence[builtins.str], typing.Sequence[builtins.bool], Any, typing.Sequence[builtins.float], Literal['ascending'], Literal['descending'], typing.Sequence[Union[builtins.dict[Any, Any], Any]], Literal['x'], Literal['y'], Literal['color'], Literal['fill'], Literal['stroke'], Literal['strokeWidth'], Literal['size'], Literal['shape'], Literal['fillOpacity'], Literal['strokeOpacity'], Literal['opacity'], Literal['text'], Literal['-x'], Literal['-y'], Literal['-color'], Literal['-fill'], Literal['-stroke'], Literal['-strokeWidth'], Literal['-size'], Literal['-shape'], Literal['-fillOpacity'], Literal['-strokeOpacity'], Literal['-opacity'], Literal['-text'], altair.utils.schemapi.UndefinedType] =, stack: Union[builtins.bool, None, Any, Literal['zero'], Literal['center'], Literal['normalize'], altair.utils.schemapi.UndefinedType] =, timeUnit: Union[builtins.dict[Any, Any], Any, Literal['year'], Literal['quarter'], Literal['month'], Literal['week'], Literal['day'], Literal['dayofyear'], Literal['date'], Literal['hours'], Literal['minutes'], Literal['seconds'], Literal['milliseconds'], Literal['utcyear'], Literal['utcquarter'], Literal['utcmonth'], Literal['utcweek'], Literal['utcday'], Literal['utcdayofyear'], Literal['utcdate'], Literal['utchours'], Literal['utcminutes'], Literal['utcseconds'], Literal['utcmilliseconds'], Literal['binnedyear'], Literal['binnedyearquarter'], Literal['binnedyearquartermonth'], Literal['binnedyearmonth'], Literal['binnedyearmonthdate'], Literal['binnedyearmonthdatehours'], Literal['binnedyearmonthdatehoursminutes'], Literal['binnedyearmonthdatehoursminutesseconds'], Literal['binnedyearweek'], Literal['binnedyearweekday'], Literal['binnedyearweekdayhours'], Literal['binnedyearweekdayhoursminutes'], Literal['binnedyearweekdayhoursminutesseconds'], Literal['binnedyeardayofyear'], Literal['binnedutcyear'], Literal['binnedutcyearquarter'], Literal['binnedutcyearquartermonth'], Literal['binnedutcyearmonth'], Literal['binnedutcyearmonthdate'], Literal['binnedutcyearmonthdatehours'], Literal['binnedutcyearmonthdatehoursminutes'], Literal['binnedutcyearmonthdatehoursminutesseconds'], Literal['binnedutcyearweek'], Literal['binnedutcyearweekday'], Literal['binnedutcyearweekdayhours'], Literal['binnedutcyearweekdayhoursminutes'], Literal['binnedutcyearweekdayhoursminutesseconds'], Literal['binnedutcyeardayofyear'], Literal['yearquarter'], Literal['yearquartermonth'], Literal['yearmonth'], Literal['yearmonthdate'], Literal['yearmonthdatehours'], Literal['yearmonthdatehoursminutes'], Literal['yearmonthdatehoursminutesseconds'], Literal['yearweek'], Literal['yearweekday'], Literal['yearweekdayhours'], Literal['yearweekdayhoursminutes'], Literal['yearweekdayhoursminutesseconds'], Literal['yeardayofyear'], Literal['quartermonth'], Literal['monthdate'], Literal['monthdatehours'], Literal['monthdatehoursminutes'], Literal['monthdatehoursminutesseconds'], Literal['weekday'], Literal['weekdayhours'], Literal['weekdayhoursminutes'], Literal['weekdayhoursminutesseconds'], Literal['dayhours'], Literal['dayhoursminutes'], Literal['dayhoursminutesseconds'], Literal['hoursminutes'], Literal['hoursminutesseconds'], Literal['minutesseconds'], Literal['secondsmilliseconds'], Literal['utcyearquarter'], Literal['utcyearquartermonth'], Literal['utcyearmonth'], Literal['utcyearmonthdate'], Literal['utcyearmonthdatehours'], Literal['utcyearmonthdatehoursminutes'], Literal['utcyearmonthdatehoursminutesseconds'], Literal['utcyearweek'], Literal['utcyearweekday'], Literal['utcyearweekdayhours'], Literal['utcyearweekdayhoursminutes'], Literal['utcyearweekdayhoursminutesseconds'], Literal['utcyeardayofyear'], Literal['utcquartermonth'], Literal['utcmonthdate'], Literal['utcmonthdatehours'], Literal['utcmonthdatehoursminutes'], Literal['utcmonthdatehoursminutesseconds'], Literal['utcweekday'], Literal['utcweeksdayhours'], Literal['utcweekdayhoursminutes'], Literal['utcweekdayhoursminutesseconds'], Literal['utcdayhours'], Literal['utcdayhoursminutes'], Literal['utcdayhoursminutesseconds'], Literal['utchoursminutes'], Literal['utchoursminutesseconds'], Literal['utcminutesseconds'], Literal['utcsecondsmilliseconds'], altair.utils.schemapi.UndefinedType] =, title: Union[builtins.str, None, typing.Sequence[builtins.str], Any, altair.utils.schemapi.UndefinedType] =, type: Union[Any, Literal['quantitative'], Literal['ordinal'], Literal['temporal'], Literal['nominal'], altair.utils.schemapi.UndefinedType] =, **kwds: Any) -> altair.vegalite.v5.schema.channels.Y"
minalt.py:8: note: Revealed type is "def (*args: Any, **kwds: Any) -> altair.vegalite.v5.schema.core.Color"
minalt.py:9: note: Revealed type is "def (data: Union[Union[builtins.dict[Any, Any], pandas.core.frame.DataFrame, altair.utils.data.SupportsGeoInterface, altair.utils.core.DataFrameLike, altair.vegalite.v5.schema.core.Data, builtins.str, altair.vegalite.v5.schema.core.Generator, Any], Any] =, encoding: Union[altair.vegalite.v5.schema.core.FacetedEncoding, Any] =, mark: Union[builtins.str, altair.vegalite.v5.schema.core.AnyMark, Any] =, width: Union[builtins.int, builtins.str, builtins.dict[Any, Any], altair.vegalite.v5.schema.core.Step, Any] =, height: Union[builtins.int, builtins.str, builtins.dict[Any, Any], altair.vegalite.v5.schema.core.Step, Any] =, **kwargs: Any) -> altair.vegalite.v5.api.Chart"
minalt.py:10: note: Revealed type is "altair.vegalite.v5.api.Chart"
minalt.py:11: note: Revealed type is "Any"
Found 1 error in 1 file (checked 1 source file)

pytype 2024.04.11
(this passes the typechecker with no complaints, so here are just the reveal_type messages)

File "/mnt/c/experiment/minalt.py", line 6, in <module>: Any [reveal-type]
File "/mnt/c/experiment/minalt.py", line 7, in <module>: Any [reveal-type]
File "/mnt/c/experiment/minalt.py", line 8, in <module>: Any [reveal-type]
File "/mnt/c/experiment/minalt.py", line 9, in <module>: Any [reveal-type]
File "/mnt/c/experiment/minalt.py", line 10, in <module>: Any [reveal-type]
File "/mnt/c/experiment/minalt.py", line 11, in <module>: Any [reveal-type]

[binste]

Thanks! Those outputs were very helpful. I think mypy at least thinks that alt.Color is alt.vegalite.v5.schema.core.Color instead of alt.vegalite.v5.schema.channels.Color due to the from * imports in https://github.com/vega/altair/blob/main/altair/vegalite/v5/schema/__init__.py#L4 where the channels overwrite core. We should probably be explicit with the imports (needs to be autogenerated) or specify it in __all__ on core.py.

Is this blocking you from using Altair or can you type: ignore it for now? Just so I know how to prioritise this.

[wyattscarpenter]

Not a blocker for me at all! As you say, I can just type ignore.