python pandas 正则表达式从另一行查找模式答案

【问题标题】：python pandas regex find pattern from another rowpython pandas 正则表达式从另一行查找模式
【发布时间】：2022-07-20 17:09:12
【问题描述】：

我有一个具有以下模式的 python pandas 数据框：

file_path
/home
/home/folder1
/home/folder1/file1.xlsx
/home/folder1/file2.xlsx
/home/folder2
/home/folder2/date
/home/folder2/date/dates.txt
/home/folder3

我想在新列中获取父路径，如果没有父路径，则将其称为“ROOT”

file_path	parent_path
/home	ROOT
/home/folder1	/home
/home/folder1/file1.xlsx	/home/folder1
/home/folder1/file2.xlsx	/home/folder1
/home/folder2	/home
/home/folder2/date	/home/folder2
/home/folder2/date/dates.txt	/home/folder2/date
/home/folder3	/home

我的尝试：

import re
import pandas as pd

df = pd.DataFrame(["/home", "/home/folder1", "/home/folder1/file1.xlsx", 
"/home/folder1/file1.xlsx", "/home/folder1/file2.xlsx", "/home/folder2", 
"/home/folder2/date", "/home/folder2/date/dates.txt", "/home/folder3"], columns=["file_path"])

# Get list

file_paths = df.file_path.unique()

def match_parent(x, file_paths):
    x = x.split('/')
    levels = len(x)
    # Check that parent contains all elements of x and the length is 1 less

我正在考虑创建一个函数：

对于每一行，计算其长度并匹配那些比当前行少 1 个长度的 AND，
之前的所有项目都匹配（完全相同）

我该怎么做？

【问题讨论】：

标签： python pandas string path

【解决方案1】：

使用pathlib.Path.parent提取父级，如下：

import pandas as pd
import pathlib

df = pd.DataFrame(["/home", "/home/folder1", "/home/folder1/file1.xlsx",
                   "/home/folder1/file1.xlsx", "/home/folder1/file2.xlsx", "/home/folder2",
                   "/home/folder2/date", "/home/folder2/date/dates.txt", "/home/folder3"], columns=["file_path"])


df["parent"] = df["file_path"].apply(lambda x: pathlib.Path(x).parent)
print(df)

输出

                      file_path              parent
0                         /home                   /
1                 /home/folder1               /home
2      /home/folder1/file1.xlsx       /home/folder1
3      /home/folder1/file1.xlsx       /home/folder1
4      /home/folder1/file2.xlsx       /home/folder1
5                 /home/folder2               /home
6            /home/folder2/date       /home/folder2
7  /home/folder2/date/dates.txt  /home/folder2/date
8                 /home/folder3               /home

【讨论】：