Python 2.7 Python将列中的子字符串替换为另一列中的子字符串

我有一个Python数据帧，如下所示：

Id      Title            URL                                       PosterPath
Id-1    Bruce Almighty   https://www.youtube.com/embed/5VGyTOGxyVA  https://i.ytimg.com/vi/XXXRRR/hqdefault.jpg
Id-2    Superhero Movie  https://www.youtube.com/embed/3BnXz-7-y-o  https://i.ytimg.com/vi/XXXRRR/hqdefault.jpg
Id-3    Taken            https://www.youtube.com/embed/vjbfiOERDYs  https://i.ytimg.com/vi/XXXRRR/hqdefault.jpg

Id      Title            URL                                       PosterPath
Id-1    Bruce Almighty   https://www.youtube.com/embed/5VGyTOGxyVA  https://i.ytimg.com/vi/5VGyTOGxyVA/hqdefault.jpg
Id-2    Superhero Movie  https://www.youtube.com/embed/3BnXz-7-y-o  https://i.ytimg.com/vi/3BnXz-7-y-o/hqdefault.jpg
Id-3    Taken            https://www.youtube.com/embed/vjbfiOERDYs  https://i.ytimg.com/vi/vjbfiOERDYs/hqdefault.jpg

我想将PosterPath列中的子字符串“XXXRRR”替换为“URL”列中“embed/”字符串之后的子字符串 输出数据帧如下所示：

Id      Title            URL                                       PosterPath
Id-1    Bruce Almighty   https://www.youtube.com/embed/5VGyTOGxyVA  https://i.ytimg.com/vi/XXXRRR/hqdefault.jpg
Id-2    Superhero Movie  https://www.youtube.com/embed/3BnXz-7-y-o  https://i.ytimg.com/vi/XXXRRR/hqdefault.jpg
Id-3    Taken            https://www.youtube.com/embed/vjbfiOERDYs  https://i.ytimg.com/vi/XXXRRR/hqdefault.jpg

Id      Title            URL                                       PosterPath
Id-1    Bruce Almighty   https://www.youtube.com/embed/5VGyTOGxyVA  https://i.ytimg.com/vi/5VGyTOGxyVA/hqdefault.jpg
Id-2    Superhero Movie  https://www.youtube.com/embed/3BnXz-7-y-o  https://i.ytimg.com/vi/3BnXz-7-y-o/hqdefault.jpg
Id-3    Taken            https://www.youtube.com/embed/vjbfiOERDYs  https://i.ytimg.com/vi/vjbfiOERDYs/hqdefault.jpg

用于：

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真棒的回答！！