print os.path.relpath("d:/MyProj/MyFile.txt")
#..\MyProj\MyFile.txt

path = "..\MyProj\MyFile.txt"
print os.path.abspath(path)
#D:\MyProj\MyFile.txt

转载于:https://www.cnblogs.com/hont/p/5412432.html

在一份代码中看到了一个路径转换的方法，贴出来共享。具体是谁的代码也不知道，如有冒犯请留言。

        /// <summary>
        /// 绝对路径转相对路径
        /// </summary>
        /// <param name="strBasePath">基本路径</param>
        /// <param name="strFullPath">绝对路径</param>
        /// <returns>strFullPath相对于strBasePath的相对路径</returns>
        public static string GetRelativePath(string strBasePath, string strFullPath)
        {
            if (strBasePath == null)
                throw new ArgumentNullException("strBasePath");

            if (strFullPath == null)
                throw new ArgumentNullException("strFullPath");
            
            strBasePath = Path.GetFullPath(strBasePath);
            strFullPath = Path.GetFullPath(strFullPath);
            
            var DirectoryPos = new int[strBasePath.Length];
            int nPosCount = 0;
            
            DirectoryPos[nPosCount] = -1;
            ++nPosCount;
            
            int nDirectoryPos = 0;
            while (true)
            {
                nDirectoryPos = strBasePath.IndexOf('\\', nDirectoryPos);
                if (nDirectoryPos == -1)
                    break;
                
                DirectoryPos[nPosCount] = nDirectoryPos;
                ++nPosCount;
                ++nDirectoryPos;
            }
            
            if (!strBasePath.EndsWith("\\"))
            {
                DirectoryPos[nPosCount] = strBasePath.Length;
                ++nPosCount;
            }     
            
            int nCommon = -1;
            for (int i = 1; i < nPosCount; ++i)
            {
                int nStart = DirectoryPos[i - 1] + 1;
                int nLength = DirectoryPos[i] - nStart;
                
                if (string.Compare(strBasePath, nStart, strFullPath, nStart, nLength, true) != 0)
                    break;
                
                nCommon = i;
            }
            
            if (nCommon == -1)
                return strFullPath;
            
            var strBuilder = new StringBuilder();
            for (int i = nCommon + 1; i < nPosCount; ++i)
                strBuilder.Append("..\\");
            
            int nSubStartPos = DirectoryPos[nCommon] + 1;
            if (nSubStartPos < strFullPath.Length)
                strBuilder.Append(strFullPath.Substring(nSubStartPos));
            
            string strResult = strBuilder.ToString();
            return strResult == string.Empty ? ".\\" : strResult;
        }

用法：

using System;
using System.Text;
using System.IO;

namespace PathDemo
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			string str = GetRelativePath ("/Users/apple/Documents/TempDemo/PathDemo", "/Users/apple/Documents/TempDemo/PathDemo/PathDemo/Main.cs");
			Console.WriteLine ("********");
			Console.WriteLine (str);
			Console.WriteLine ("********");
		}

		public static string GetRelativePath(string strBasePath, string strFullPath)
		{
			if (strBasePath == null)
				throw new ArgumentNullException("strBasePath");
			
			if (strFullPath == null)
				throw new ArgumentNullException("strFullPath");
			
			strBasePath = Path.GetFullPath(strBasePath);
			strFullPath = Path.GetFullPath(strFullPath);
			
			var DirectoryPos = new int[strBasePath.Length];
			int nPosCount = 0;
			
			DirectoryPos[nPosCount] = -1;
			++nPosCount;
			
			int nDirectoryPos = 0;
			while (true)
			{
				nDirectoryPos = strBasePath.IndexOf('\\', nDirectoryPos);
				if (nDirectoryPos == -1)
					break;
				
				DirectoryPos[nPosCount] = nDirectoryPos;
				++nPosCount;
				++nDirectoryPos;
			}
			
			if (!strBasePath.EndsWith("\\"))
			{
				DirectoryPos[nPosCount] = strBasePath.Length;
				++nPosCount;
			}     
			
			int nCommon = -1;
			for (int i = 1; i < nPosCount; ++i)
			{
				int nStart = DirectoryPos[i - 1] + 1;
				int nLength = DirectoryPos[i] - nStart;
				
				if (string.Compare(strBasePath, nStart, strFullPath, nStart, nLength, true) != 0)
					break;
				
				nCommon = i;
			}
			
			if (nCommon == -1)
				return strFullPath;
			
			var strBuilder = new StringBuilder();
			for (int i = nCommon + 1; i < nPosCount; ++i)
				strBuilder.Append("..\\");
			
			int nSubStartPos = DirectoryPos[nCommon] + 1;
			if (nSubStartPos < strFullPath.Length)
				strBuilder.Append(strFullPath.Substring(nSubStartPos));
			
			string strResult = strBuilder.ToString();
			return strResult == string.Empty ? ".\\" : strResult;
		}
	}
}