您如何在Python中获取文件的绝对路径？

Question

I have read quite a few links on the site saying to use "os.path.abspath(#filename)". This method isn't exactly working for me. I am writing a program that will be able to search a given directory for files with certain extensions, save the name and absolute path as keys and values (respectively) into a dictionary, and then use the absolute path to open the files and make the edits that are required. The problem I am having is that when I use os.path.abspath() it isn't returning the full path.

Let's say my program is on the desktop. I have a file stored at "C:\\Users\\Travis\\Desktop\\Test1\\Test1A\\test.c". My program can easily locate this file, but when I use os.path.abspath() it returns "C:\\Users\\Travis\\Desktop\\test.c" which is the absolute path of where my source code is stored, but not the file I was searching for.

My exact code is:

import os
Files={}#Dictionary that will hold file names and absolute paths
root=os.getcwd()#Finds starting point
for root, dirs, files in os.walk(root):
    for file in files:
        if file.endswith('.c'):#Look for files that end in .c
            Files[file]=os.path.abspath(file)

Any tips or advice as to why it may be doing this and how I can fix it? Thanks in advance!

Answer 1

os.path.abspath() makes a relative path absolute relative to the current working directory , not to the file's original location. A path is just a string, Python has no way of knowing where the filename came from.

You need to supply the directory yourself. When you use os.walk , each iteration lists the directory being listed ( root in your code), the list of subdirectories (just their names) and a list of filenames (again, just their names). Use root together with the filename to make an absolute path:

Files={}
cwd = os.path.abspath(os.getcwd())
for root, dirs, files in os.walk(cwd):
    for file in files:
        if file.endswith('.c'):
            Files[file] = os.path.join(root, os.path.abspath(file))

Note that your code only records the one path for each unique filename; if you have foo/bar/baz.c and foo/spam/baz.c , it depends on the order the OS listed the bar and spam subdirectories which one of the two paths wins.

You may want to collect paths into a list instead:

Files={}
cwd = os.path.abspath(os.getcwd())
for root, dirs, files in os.walk(cwd):
    for file in files:
        if file.endswith('.c'):
            full_path = os.path.join(root, os.path.abspath(file))
            Files.setdefault(file, []).append(full_path)

Answer 2

Per the docs for os.path.join ,

If any component is an absolute path, all previous components (on Windows, including the previous drive letter, if there was one) are thrown away

So, for example, if the second argument is an absolute path, the first path, '/a/b/c' is discarded.

In [14]: os.path.join('/a/b/c', '/d/e/f')
Out[14]: '/d/e/f'

Therefore,

os.path.join(root, os.path.abspath(file))

will discard root no matter what it is, and return os.path.abspath(file) which will tack file on to the current working directory, which will not necessarily be the same as root .

Instead, to form the absolute path to the file:

fullpath = os.path.abspath(os.path.join(root, file))

Actually, I believe the os.path.abspath is unnecessary, since I believe root will always be absolute, but my reasoning for that depends on the source code for os.walk not just the documented (guaranteed) behavior of os.walk . So to be absolutely sure (pun intended), use os.path.abspath .

---

import os
samefiles = {}
root = os.getcwd()
for root, dirs, files in os.walk(root):
    for file in files:
        if file.endswith('.c'):
            fullpath = os.path.join(root, file)
            samefiles.setdefault(file, []).append(fullpath) 

print(samefiles)

Answer 3

Glob is useful in these cases, you can do:

files = {f:os.path.join(os.getcwd(), f) for f in glob.glob("*.c")}

to get the same result