Importing Modules
Module Search Path
The Python interpreter searches for modules in a specific order, defined by the sys.path
variable. This is crucial for importing modules correctly.
sys.path
is a list of strings, each representing a directory. The interpreter searches these directories in order until it finds the module being imported.
import sys
print(sys.path)
The sys.path
list typically includes:
- The directory containing the script being run (or the current directory if no script is specified).
- The directories specified by the
PYTHONPATH
environment variable (if set). - Installation-dependent default locations (e.g., site-packages directories).
PYTHONPATH Environment Variable
If a module is not found in any of these directories, an ImportError
is raised.
Modifying sys.path
:
You can modify sys.path
programmatically to add or remove directories from the search path. This is useful for:
- Importing modules from custom locations.
- Managing different versions of modules.
Example: adding a custom directory:
import sys
sys.path.append('/path/to/my/modules') # replace with your path
import my_module # now you can import your module
Important Considerations:
- Order Matters: The order of directories in
sys.path
is significant. The interpreter will find the first occurrence of the module. - Namespace Conflicts: Modifying
sys.path
can lead to namespace conflicts if you have multiple modules with the same name in different directories. - Security: Avoid arbitrarily adding directories to
sys.path
from untrusted sources, as this could expose your system to malicious code. Be especially cautious with dynamically constructed paths.