chapter 23: Unix

23.1 path

full path

Get a full absolute path a file

import os
def full_path(file):
    return os.path.abspath(os.path.expanduser(file))

join with slash

Both URL and file path joins use slashes as dividers between their parts. For example:

path/to/dir + file --> path/to/dir/file path/to/dir/ + file --> path/to/dir/file http://algorithms.com/ + part --> http://algorithms.com/part http://algorithms.com + part --> http://algorithms/part

import os

def join_with_slash(base, suffix):
    # Remove / trailing
    base = base.rstrip('/')
    # Remove / leading
    suffix = suffix.lstrip('/').rstrip()
    full_path = "{}/{}".format(base, suffix)
    return full_path

simplify path

Given an absolute path for a file (Unix-style), simplify it.

For example, path = "/home/", => "/home" path = "/a/./b/../../c/", => "/c"

Corner Cases:

Did you consider the case where path = "/../"? In this case, you should return "/". Another corner case is the path might contain multiple slashes '/' together, such as "/home//foo/". In this case, you should ignore redundant slashes and return "/home/foo".

Reference: https://leetcode.com/problems/simplify-path/description/

import os
def simplify_path_v1(path):
    return os.path.abspath(path)

def simplify_path_v2(path):
    stack, tokens = [], path.split("/")
    for token in tokens:
        if token == ".." and stack:
            stack.pop()
        elif token != ".." and token != "." and token:
            stack.append(token)
    return "/" + "/".join(stack)

split

Splitting a path into 2 parts Example: Input: https://algorithms/unix/test.py (for url) Output:

part[0]: https://algorithms/unix part[1]: test.py

Input: algorithms/unix/test.py (for file path) Output:

part[0]: algorithms/unix part[1]: test.py

import os

def split(path):
    parts = []
    split_part = path.rpartition('/')
    # Takt the origin path without the last part
    parts.append(split_part[0])
    # Take the last element of list
    parts.append(split_part[2])
    return parts