Check Type: How to check if something is a RDD or a dataframe?

问题

I'm using python, and this is Spark Rdd/dataframes.

I tried isinstance(thing, RDD) but RDD wasn't recognized.

The reason I need to do this:

I'm writing a function where both RDD and dataframes could be passed in, so I'll need to do input.rdd to get the underlying rdd if a dataframe is passed in.

回答1:

isinstance will work just fine:

from pyspark.sql import DataFrame
from pyspark.rdd import RDD

def foo(x):
    if isinstance(x, RDD):
        return "RDD"
    if isinstance(x, DataFrame):
        return "DataFrame"

foo(sc.parallelize([]))
## 'RDD'
foo(sc.parallelize([("foo", 1)]).toDF())
## 'DataFrame'

but single dispatch is much more elegant approach:

from functools import singledispatch

@singledispatch
def bar(x):
    pass 

@bar.register(RDD)
def _(arg):
    return "RDD"

@bar.register(DataFrame)
def _(arg):
    return "DataFrame"

bar(sc.parallelize([]))
## 'RDD'

bar(sc.parallelize([("foo", 1)]).toDF())
## 'DataFrame'

If you don't mind additional dependencies multipledispatch is also an interesting option:

from multipledispatch import dispatch

@dispatch(RDD)
def baz(x):
    return "RDD"

@dispatch(DataFrame)
def baz(x):
    return "DataFrame"

baz(sc.parallelize([]))
## 'RDD'

baz(sc.parallelize([("foo", 1)]).toDF())
## 'DataFrame'

Finally the most Pythonic approach is to simply check an interface:

def foobar(x):
    if hasattr(x, "rdd"):
        ## It is a DataFrame
    else:
        ## It (probably) is a RDD

回答2:

another way to check is type

type(object)

that return the type of the object like

pyspark.sql.dataframe.DataFrame

来源：https://stackoverflow.com/questions/36731365/check-type-how-to-check-if-something-is-a-rdd-or-a-dataframe