input: Write a python function to create and activate a virtual environment in Python, and install project dependencies from a requirements file.
  assert create_and_activate_virtualenv('my_project') == True
output: def create_and_activate_virtualenv(project_name):
      import os
      import subprocess
      import sys
  
      # Create a virtual environment
      venv_path = os.path.join(project_name, 'venv')
      try:
          subprocess.check_call([sys.executable, '-m', 'venv', venv_path])
      except subprocess.CalledProcessError:
          return False
  
      # Activate the virtual environment
      activate_script = os.path.join(venv_path, 'Scripts', 'activate_this.py') if os.name == 'nt' else os.path.join(venv_path, 'bin', 'activate')
      
      if not os.path.exists(activate_script):
          return False
  
      # Install dependencies from the requirements.txt file
      requirements_file = os.path.join(project_name, 'requirements.txt')
      if os.path.exists(requirements_file):
          pip_executable = os.path.join(venv_path, 'Scripts', 'pip') if os.name == 'nt' else os.path.join(venv_path, 'bin', 'pip')
          try:
              subprocess.check_call([pip_executable, 'install', '-r', requirements_file])
          except subprocess.CalledProcessError:
              return False
  
      return True