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<pre><code>import pandas as pd
df = pd.DataFrame([['NewJersy',0,'2020-08-29'],
['NewJersy',12,'2020-08-30'],
['NewJersy',12,'2020-08-31'],
['NewJersy',None,'2020-09-01'],
['NewJersy',None,'2020-09-02'],
['NewJersy',None,'2020-09-03'],
['NewJersy',5,'2020-09-04'],
['NewJersy',5,'2020-09-05'],
['NewJersy',None,'2020-09-06'],
['NewYork',None,'2020-08-29'],
['NewYork',None,'2020-08-30'],
['NewYork',8,'2020-08-31'],
['NewYork',7,'2020-09-01'],
['NewYork',None,'2020-09-02'],
['NewYork',None,'2020-09-03']],
columns=['FName', 'FVal', 'GDate'])
print(df)
</code></pre>
<p>我想用以前的记录值填充空值。例如,对于20-09-01到20-09-03,列FValue的值为NULL。空值应替换为先前有效值(即20-08-31)中的值12</p>
<p>此外,如果日期2020-08-29的值为空,则应将其替换为零,因为它是第一个日期,并且没有以前的记录</p>
<p>我尝试了下面的代码,但没有工作</p>
<p>df['F']=df['F'].fillna(方法='ffill')</p>
<p>检查此处的预期值:
<a href="https://i.stack.imgur.com/CRvVy.png" rel="nofollow noreferrer">Fill Null Values image</a></p>
<p>谢谢</p>