如何在熊猫数据框中仅将单个数字替换为另一个数字?
问题描述：
我有以下熊猫数据框:
date
0 1
1 2
2 23
3 31
4 4
...
n 3
如何仅用以下格式替换从1到9的所有数字(例如，具有一位数字的数字):
How can I only replace all the numbers from 1 to 9 (e.g. numbers with one digit) with the following format:
01, 02, 03, 04, 05, 06, 07, 08, 09
我尝试使用以下熊猫替换功能:
I tried to do with pandas replace function the following:
df['date'] = df['date'].replace(['1', '2', '3', '4', '5', '6', '7', '8', '9']),
[' 01 ', ' 02 ', ' 03 ', '04 ', ' 05 ', ' 06 ', ' 07 ', ' 08 ', ' 09 '],regex=True)
但是，它没有作用，因为它正在修改全部(即数字多于一个的数字)数据框内的数字.因此，如何规范日期列?
However, it didn't worked because it is modifying all (i.e. numbers with more than one digit) the numbers inside the dataframe. Thus, how can I normalize the date column?.
答
如果需要，使用astype(str)将列强制转换为str，然后调用
If needed cast the column to str using astype(str), then call str.zfill to 0 pad those numbers:
In [13]:
df['date'] = df['date'].astype(str).str.zfill(2)
df
Out[13]:
date
0 01
1 02
2 23
3 31
4 04
关于您的评论:
In [17]:
df['year'] = '20' + df['date']
df
Out[17]:
date year
0 01 2001
1 02 2002
2 23 2023
3 31 2031
4 04 2004
当列dtype已经是str
the above works when the column dtype is already str