pandas :将dtype'object'转换为int [英] Pandas: convert dtype 'object' to int

问题描述

我已经读了一个查询到Pandas的SQL查询，尽管它们是字符串，日期和整数，但它们的值作为dtype'object'传入.我可以将日期"object"转换为Pandas datetime dtype，但是在尝试转换字符串和整数时遇到错误.

I've read an SQL query into Pandas and the values are coming in as dtype 'object', although they are strings, dates and integers. I am able to convert the date 'object' to a Pandas datetime dtype, but I'm getting an error when trying to convert the string and integers.

这里是一个例子:

>>> import pandas as pd
>>> df = pd.read_sql_query('select * from my_table', conn)
>>> df
    id    date          purchase
 1  abc1  2016-05-22    1
 2  abc2  2016-05-29    0
 3  abc3  2016-05-22    2
 4  abc4  2016-05-22    0

>>> df.dtypes
 id          object
 date        object
 purchase    object
 dtype: object

将df['date']转换为日期时间是可行的:

Converting the df['date'] to a datetime works:

>>> pd.to_datetime(df['date'])
 1  2016-05-22
 2  2016-05-29
 3  2016-05-22
 4  2016-05-22
 Name: date, dtype: datetime64[ns] 

但是尝试将df['purchase']转换为整数时出现错误:

But I get an error when trying to convert the df['purchase'] to an integer:

>>> df['purchase'].astype(int)
 ....
 pandas/lib.pyx in pandas.lib.astype_intsafe (pandas/lib.c:16667)()
 pandas/src/util.pxd in util.set_value_at (pandas/lib.c:67540)()

 TypeError: long() argument must be a string or a number, not 'java.lang.Long'

注意:我尝试.astype('float')

当尝试转换为字符串时，似乎什么也没发生.

And when trying to convert to a string, nothing seems to happen.

>>> df['id'].apply(str)
 1 abc1
 2 abc2
 3 abc3
 4 abc4
 Name: id, dtype: object

推荐答案

根据@piRSquared的评论记录对我有用的答案.

Documenting the answer that worked for me based on the comment by @piRSquared.

我需要先转换为字符串，然后转换为整数.

I needed to convert to a string first, then an integer.

>>> df['purchase'].astype(str).astype(int)

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