Pyspark Creating timestamp column

问题

I am using spark 2.1.0. I am not able to create timestamp column in pyspark I am using below code snippet. Please help

df=df.withColumn('Age',lit(datetime.now()))

I am getting

assertion error:col should be Column

Please help

回答1:

Assuming you have dataframe from your code snippet and you want same timestamp for all your rows.

Let me create some dummy dataframe.

>>> dict = [{'name': 'Alice', 'age': 1},{'name': 'Again', 'age': 2}]
>>> df = spark.createDataFrame(dict)

>>> import time
>>> import datetime
>>> timestamp = datetime.datetime.fromtimestamp(time.time()).strftime('%Y-%m-%d %H:%M:%S')
>>> type(timestamp)
<class 'str'>

>>> from pyspark.sql.functions import lit,unix_timestamp
>>> timestamp
'2017-08-02 16:16:14'
>>> new_df = df.withColumn('time',unix_timestamp(lit(timestamp),'yyyy-MM-dd HH:mm:ss').cast("timestamp"))
>>> new_df.show(truncate = False)
+---+-----+---------------------+
|age|name |time                 |
+---+-----+---------------------+
|1  |Alice|2017-08-02 16:16:14.0|
|2  |Again|2017-08-02 16:16:14.0|
+---+-----+---------------------+

>>> new_df.printSchema()
root
 |-- age: long (nullable = true)
 |-- name: string (nullable = true)
 |-- time: timestamp (nullable = true)

回答2:

I am not sure for 2.1.0, on 2.2.1 at least you can just:

from pyspark.sql import functions as F
df.withColumn('Age', F.current_timestamp())

Hope it helps!

来源：https://stackoverflow.com/questions/45469438/pyspark-creating-timestamp-column