The Problem

You’ve installed a Python module using pip, easy_install, or python setup.py install. The installation reports success, but when you try to import it, Python throws:

>>> import mechanize
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named mechanize

This is confusing because the installation appeared to succeed.

The Most Likely Cause: Permissions

In many cases, the module did install, but it was placed in a directory where only root has read/write permission.

That means:

• The package exists on disk.
• Your normal user account cannot read it.
• Python, running as your user, can’t import it—hence the error.

This often happens if you run:

sudo pip install mechanize

Instead of installing for your user.

The Fix: Correct Permissions or Reinstall for User

1. Check permissions

Find where the module is installed:

python -m site
# or
pip show mechanize

Inspect the directory with:

ls -ld /usr/local/lib/python2.7/dist-packages/mechanize*

If you see root root as the owner, that’s the problem.

2. Fix permissions

Option A — Change ownership to your user:

sudo chown -R $USER:$USER /usr/local/lib/python2.7/dist-packages/mechanize*

Option B — Add read permission for all users:

sudo chmod -R a+rX /usr/local/lib/python2.7/dist-packages/mechanize*

3. Safer: Reinstall without sudo

A better long-term fix is to install packages without root privileges:

# Install in your user’s home directory
pip install --user mechanize

This places the module in ~/.local/lib/pythonX.Y/site-packages/, where your user has full access.

Other Possible Causes

If permissions aren’t the issue, check:

1. Wrong Python version
   • Installed with pip3 but running python2, or vice versa.
2. Multiple environments
   • Virtualenv, Conda, or system Python confusion.
3. Path issues
   • Module installed in a path not included in sys.path.
4. Unsupported library versions
   • Some packages (like mechanize) only support Python 2.7, not Python 3.

Conclusion

The most common cause of ImportError: No module named … after a “successful” install is a permission mismatch: the module is installed, but your user can’t access it because it was written as root.

👉 Fix it by correcting permissions or reinstalling with pip install --user. If that doesn’t work, double-check your Python version, environments, and sys.path.

Once permissions are corrected, your import mechanize (or any other library) will work as expected.