getting unusual error when creating a string schema type dataframe

I am creating a simple data frame.

df=spark.createDataFrame(data=[('11s1 ab')],schema=['str'])

I get error:

TypeError: Can not infer schema for type: <class ‘str’>

However if I change the statement to :

df=spark.createDataFrame(data=[('11s1 ab',)],schema=['str'])

my dataframe is successfully created.

I want to understand why that comma sign matters in data definition tuple in spark.createdataFrame.

>Solution :

In the document of createDataFrame you can see the data field must be:

data: Union[pyspark.rdd.RDD[Any], Iterable[Any], ForwardRef('PandasDataFrameLike')]

(1,) or [1] are iterable but (1) would be integer type which is not iterable