Design File System in Python

Suppose we have to design a file system which provides these two functions −

1. createPath(path, value) − This creates a new path and associates a value to it if possible and returns True. It returns False if the path already exists or its parent path doesn't exist.
2. get(path) − This finds the value associated with a path or returns -1 if the path doesn't exist.

The format of a path is one or more concatenated strings of the form − (forward slash) / followed by one or more lowercase English letters. For example, /programming and /programming/problems are valid paths while an empty string and / are not. Here we have to implement these two functions.

So as input, if we create a file-system, then create a path using [‘/a’, 1], then after using get(), with parameter [‘/a’], the output will be 1.

To solve this, we will follow these steps −

• Define a map d
• The createPath method will take path and value, this will act like −
• p := list of components of path split by ‘/’
• x := d
• for i in range 1 to length of p – 1
  • if p[i] is not present in x, then return false
  • x := x[p[i]][1]
• if last element of p is in x, then return false
• x[last element of p] := a list with v and empty map
• return true
• The get() method is taking the path
• x := d
• p := list of components of path split by ‘/’
• for i in range 1 to length of p – 1
  • if p[i] is not present in x, then return -1
  • x := x[p[i]][1]
• if last element of p is in x, then return x[last element of p][0], otherwise return -1

Example(Python)

Let us see the following implementation to get a better understanding −

class FileSystem(object):
   def __init__(self):
      self.d = {}
   def create(self, p, v):
      p = p.split("/")
      x = self.d
      for i in range(1,len(p)-1):
         if p[i] not in x:
            return False
         x = x[p[i]][1]
      if p[-1] in x:
         return False
      x[p[-1]] = [v,{}]
      return True
   def get(self, p):
      x = self.d
      p = p.split("/")
      for i in range(1,len(p)-1):
         if p[i] not in x:
            return -1
         x= x[p[i]][1]
      if p[-1] in x:
         return x[p[-1]][0]
      else:
         return -1
ob = FileSystem()
print(ob.create("/a", 1))
print(ob.get("/a"))

Input

Initialize the object, then call createPath(“/a”, 1) and get(“/a”)

Output

True
1