我在这里查找了这个问题,但之前的解决方案对我没有用。我有一个这样格式的数据框:
mdf.head()
dbn boro bus
0 17K548 Brooklyn B41, B43, B44-SBS, B45, B48, B49, B69
1 09X543 Bronx Bx13, Bx15, Bx17, Bx21, Bx35, Bx4, Bx41, Bx4A,...
4 28Q680 Queens Q25, Q46, Q65
6 14K474 Brooklyn B24, B43, B48, B60, Q54, Q59
还有几列,但我已将它们排除在外(地铁线和测试分数)。 当我尝试将此DataFrame转换为Spark DataFrame时,会出现以下错误。
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-30-1721be5c2987> in <module>()
----> 1 sparkdf = sqlc.createDataFrame(mdf)
/usr/local/Cellar/apache-spark/1.6.2/libexec/python/pyspark/sql/context.pyc in createDataFrame(self, data, schema, samplingRatio)
423 rdd, schema = self._createFromRDD(data, schema, samplingRatio)
424 else:
--> 425 rdd, schema = self._createFromLocal(data, schema)
426 jrdd = self._jvm.SerDeUtil.toJavaArray(rdd._to_java_object_rdd())
427 jdf = self._ssql_ctx.applySchemaToPythonRDD(jrdd.rdd(), schema.json())
/usr/local/Cellar/apache-spark/1.6.2/libexec/python/pyspark/sql/context.pyc in _createFromLocal(self, data, schema)
339
340 if schema is None or isinstance(schema, (list, tuple)):
--> 341 struct = self._inferSchemaFromList(data)
342 if isinstance(schema, (list, tuple)):
343 for i, name in enumerate(schema):
/usr/local/Cellar/apache-spark/1.6.2/libexec/python/pyspark/sql/context.pyc in _inferSchemaFromList(self, data)
239 warnings.warn("inferring schema from dict is deprecated,"
240 "please use pyspark.sql.Row instead")
--> 241 schema = reduce(_merge_type, map(_infer_schema, data))
242 if _has_nulltype(schema):
243 raise ValueError("Some of types cannot be determined after inferring")
/usr/local/Cellar/apache-spark/1.6.2/libexec/python/pyspark/sql/types.pyc in _merge_type(a, b)
860 nfs = dict((f.name, f.dataType) for f in b.fields)
861 fields = [StructField(f.name, _merge_type(f.dataType, nfs.get(f.name, NullType())))
--> 862 for f in a.fields]
863 names = set([f.name for f in fields])
864 for n in nfs:
/usr/local/Cellar/apache-spark/1.6.2/libexec/python/pyspark/sql/types.pyc in _merge_type(a, b)
854 elif type(a) is not type(b):
855 # TODO: type cast (such as int -> long)
--> 856 raise TypeError("Can not merge type %s and %s" % (type(a), type(b)))
857
858 # same type
TypeError: Can not merge type <class 'pyspark.sql.types.StringType'> and <class 'pyspark.sql.types.DoubleType'>
根据我所了解的,这可能是由于标题被视为数据而导致的问题。据我所知,您无法从DataFrame中删除标题,因此我该如何解决此错误并将此DataFrame转换为Spark DataFrame?
编辑:以下是我创建Pandas DF并解决问题的代码。
sqlc = SQLContext(sc)
df = pd.DataFrame(pd.read_csv('hsdir.csv', encoding = 'utf_8_sig'))
df = df[['dbn', 'boro', 'bus', 'subway', 'total_students']]
df1 = pd.DataFrame(pd.read_csv('sat_r.csv', encoding = 'utf_8_sig'))
df1 = df1.rename(columns = {'Num of SAT Test Takers': 'num_test_takers', 'SAT Critical Reading Avg. Score': 'read_avg', 'SAT Math Avg. Score' : 'math_avg', 'SAT Writing Avg. Score' : 'write_avg'})
mdf = pd.merge(df, df1, left_on = 'dbn', right_on = 'DBN', how = 'left')
mdf = mdf[pd.notnull(mdf['DBN'])]
mdf.to_csv('merged.csv', encoding = 'utf-8')
ndf = sqlContext.read.format("com.databricks.spark.csv").option("header", "true").option("inferSchema", "true").load("merged.csv")
这段代码的最后一行,从我的本地机器加载它最终使我能够将CSV正确转换为数据框,但我的问题仍然存在。为什么一开始它不能工作?
AttributeError: 'DataFrame' object has no attribute 'map'
。 - gold_cymdf
是一个 pandas DataFrame 吗?我错误地认为它是一个 Spark RDD。你需要使用 pandas 吗?或者你可以创建一个 Spark RDD,然后像上面那样将其转换为 Spark DataFrame 吗? - user4601931com.databricks.spark.csv
将其作为RDD加载以读取CSV文件,则它会完全忽略dbn列并将所有内容向左移动一列。我不确定如何避免这个问题,所以我通过Pandas的read_csv
加载了它,这样可以保留原始CSV的格式。 - gold_cyspark.read.csv("/path/to/file.csv", header=True)
,但是没有成功? - user4601931read.csv
直接内联到程序中了。问题在于我假设CSV具有编码字符和/或尾随/前导空格。我将在帖子中更新如何创建pandas框架。我还可以通过使用适当的编码将其保存在本地计算机上来解决问题,但这可能不是Apache Spark的良好实践。 - gold_cy