I have one dataframe:

```
import pandas as pd 
df1 = pd.DataFrame([['Tom', 'good', 3],
                       ['Jack', 'bad', 6],
                       ['Tom', 'average', 9],
                       ['Jerry', 'good', 89],
                       ['Lucy', 'average', 11]
                       ],
                      columns=['name', 'text', 'day'])

```

and the other dataframe:

```
df2 = pd.DataFrame([['Tom', 'bad', 55],
                   ['Jack', 'good', 64],
                   ['Mary', 'bad', 92],
                   ['Lucy', 'average', 109]
                   ],
                  columns=['name', 'text', 'day'])

```

if `df2['name']` is in `df1['name']`, then the value of '`day`' of `df1` should be replaced by that of `df2`, which means, I have the following result:

```
result = pd.DataFrame([['Tom', 'good', 55],
                   ['Jack', 'bad', 64],
                   ['Tom', 'average', 55],
                   ['Jerry', 'good', 89],
                   ['Lucy', 'average', 109]
                   ],
                  columns=['name', 'text', 'day'])

```

I know `update` can do that, but I want a conditional replacement method.