toDoublefunc = UserDefinedFunction(lambda x: x,DoubleType())
changedTypedf = joindf.withColumn("label",toDoublefunc(joindf['show']))

changedTypedf = joindf.withColumn("show", joindf["show"].cast(DoubleType()))

toDoublefunc = UserDefinedFunction(lambda x: float(x),DoubleType())
changedTypedf = joindf.withColumn("label",toDoublefunc(joindf['show']))

{ "x": 12, "y": { "p": { "name": "abc", "value": "10" }, "q":{"name":"xyz",
 "val":"99"} } }