a path class written in Python (with some test cases)

python_cd.py

class Path:
    def __init__(self, path):
        self.current_path = path

    def cd(self, new_path):
        positions = self.current_path.split('/')
        
        if new_path == '/..':
            return None
        
        if new_path[:2] == '..':
            # start with ..
            # parent path       
            parent_path = ''.join(str(p)+'/' for p in positions[:-1])[:-1]
            self.current_path = parent_path+new_path[2:]
        else:
                        
            if '..' in new_path:
                # contain parent path
                parts = new_path.split('..')
                if new_path[:4] == '/../':
                    self.current_path = parts[1]
                elif new_path[0] != '/':
                    # relative path
                    pa = self.current_path + '/' + parts[0][:-1]
                    self.current_path = ''.join(str(p)+'/' for p in pa.split('/')[:-1])+parts[1][1:]
                else:
                    # absolute path
                    pa = parts[0][:-1]
                    self.current_path = ''.join(str(p)+'/' for p in pa.split('/')[:-1])+parts[1][1:]
            else:
                # not conatin parent path
                if new_path[0] != '/':
                    # relative path
                    self.current_path += '/'+new_path
                else: 
                    self.current_path = new_path

                

path = Path('/a/b/c/d')
path.cd('/a/b/c/d/f')
print(path.current_path)
path.cd('d')
print(path.current_path)
path.cd('../ff/dd')
print(path.current_path)
path.cd('..')
print(path.current_path)

path.cd('/../as')
print(path.current_path) 

path.cd('/a/b/c/d/f')
path.cd('/..')
print(path.current_path)

path.cd('a/b/../c/d/f')
print(path.current_path)

path.cd('/a/b/../c/d/f')
print(path.current_path)

path.cd('/a/b/c/d/f')
path.cd('../asd')
print(path.current_path)

results

/a/b/c/d/f
/a/b/c/d/f/d
/a/b/c/d/f/ff/dd
/a/b/c/d/f/ff
/as
/a/b/c/d/f
/a/b/c/d/f/a/c/d/f
/a/c/d/f
/a/b/c/d/asd