diff --git a/labscript_utils/__init__.py b/labscript_utils/__init__.py
index ca52676..35868e1 100644
--- a/labscript_utils/__init__.py
+++ b/labscript_utils/__init__.py
@@ -47,6 +47,9 @@ def import_or_reload(modulename):
     return module
 
 
+from labscript_utils.versions import VersionException, check_version
+
+
 def dedent(s):
     """Remove leading spaces from the first line of a string, all common leading
     indentation (spaces only) from subsequent lines, strip trailing spaces from all
diff --git a/labscript_utils/versions.py b/labscript_utils/versions.py
new file mode 100644
index 0000000..0b84ed5
--- /dev/null
+++ b/labscript_utils/versions.py
@@ -0,0 +1,203 @@
+#####################################################################
+#                                                                   #
+# versions.py                                                       #
+#                                                                   #
+# Copyright 2019, Chris Billington                                  #
+#                                                                   #
+# This file is part of the labscript suite (see                     #
+# http://labscriptsuite.org) and is licensed under the Simplified   #
+# BSD License. See the license.txt file in the root of the project  #
+# for the full license.                                             #
+#                                                                   #
+#####################################################################
+import sys
+import os
+import importlib
+import tokenize
+import ast
+import setuptools_scm
+import packaging.version
+
+try:
+    import importlib.metadata as importlib_metadata
+except ImportError:
+    import importlib_metadata
+
+
+class NotFound(object):
+    pass
+
+
+class NoVersionInfo(object):
+    pass
+
+
+class VersionException(RuntimeError):
+    pass
+
+
+class BrokenInstall(RuntimeError):
+    pass
+
+
+ERR_BROKEN_INSTALL = """Multiple metadata files for {package} found in {path}; cannot
+reliably get version information. This indicates a previous version of the package was
+not properly removed. You may want to uninstall the package, manually delete remaining
+metadata files/folders, then reinstall the package.""".replace('\n', ' ')
+
+
+def get_import_path(import_name):
+    """Get which entry in sys.path a module would be imported from, without importing
+    it."""
+    spec = importlib.util.find_spec(import_name)
+    if spec is None:
+        raise ModuleNotFoundError(import_name)
+    location = spec.origin
+    if location is None:
+        # A namespace package
+        msg = "Version checking of namespace packages not implemented"
+        raise NotImplementedError(msg)
+    if spec.parent:
+        # A package:
+        return os.path.dirname(os.path.dirname(location))
+    else:
+        # A single-file module:
+        return os.path.dirname(location)
+
+
+def _get_metadata_version(project_name, import_path):
+    """Return the metadata version for a package with the given project name located at
+    the given import path, or None if there is no such package."""
+    
+    for finder in sys.meta_path:
+        if hasattr(finder, 'find_distributions'):
+            context = importlib_metadata.DistributionFinder.Context(
+                name=project_name, path=[import_path]
+            )
+            dists = finder.find_distributions(context)
+            dists = list(dists)
+            if len(dists) > 1:
+                msg = ERR_BROKEN_INSTALL.format(package=project_name, path=import_path)
+                raise BrokenInstall(msg)
+            if dists:
+                return dists[0].version
+
+
+def _get_literal_version(filename):
+    """Tokenize a source file and return any __version__ = <version> literal defined in
+    it.
+    """
+    if not os.path.exists(filename):
+        return None
+    with open(filename, 'r') as f:
+        try:
+            tokens = list(tokenize.generate_tokens(f.readline))
+        except tokenize.TokenError:
+            tokens = []
+        for i, token in enumerate(tokens[:-2]):
+            token_type, token_str, _, _, _ = token
+            if token_type == tokenize.NAME and token_str == '__version__':
+                next_token_type, next_token_str, _, _, _ = tokens[i + 1]
+                if next_token_type == tokenize.OP and next_token_str == '=':
+                    next_next_token_type, next_next_token_str, _, _, _ = tokens[i + 2]
+                    if next_next_token_type == tokenize.STRING:
+                        try:
+                            version = ast.literal_eval(next_next_token_str)
+                            if version is not None:
+                                return version
+                        except (SyntaxError, ValueError):
+                            continue
+
+
+def get_version(import_name, project_name=None, import_path=None):
+    """Try very hard to get the version of a package without importing it. if
+    import_path is not given, first find where it would be imported from, without
+    importing it. Then look for metadata in the same import path with the given project
+    name (note: this is not always the same as the import name, it is the name for
+    example you would ask pip to install). If that is found, return the version info
+    from it. Otherwise look for a __version__.py file in the package directory, or a
+    __version__ = <version> literal defined in the package source (without executing
+    it).
+
+    Return NotFound if the package cannot be found, and NoVersionInfo if the version
+    cannot be obtained in the above way, or if it was found but was None."""
+    if project_name is None:
+        project_name = import_name
+    if '.' in import_name:
+        msg = "Version checking of top-level packages only implemented"
+        raise NotImplementedError(msg)
+    if import_path is None:
+        # Find the path where the module lives:
+        try:
+            import_path = get_import_path(import_name)
+        except ImportError:
+            return NotFound
+    if not os.path.exists(os.path.join(import_path, import_name)):
+        return NotFound
+    try:
+        # Check if setuptools_scm gives us a version number, for the case that it's a
+        # git repo or PyPI tarball:
+        return setuptools_scm.get_version(import_path)
+    except LookupError:
+        pass
+    # Check if importlib_metadata knows about this module:
+    version = _get_metadata_version(project_name, import_path)
+    if version is not None:
+        return version
+    # Check if it has a version literal defined in a __version__.py file:
+    version_dot_py = os.path.join(import_path, import_name, '__version__.py')
+    version = _get_literal_version(version_dot_py)
+    if version is not None:
+        return version
+    # check if it has a __version__ literal defined in its main module.
+    pkg = os.path.join(import_path, import_name)
+    if os.path.isdir(pkg):
+        module_file = os.path.join(pkg, '__init__.py')
+    else:
+        module_file = pkg + '.py'
+    version = _get_literal_version(module_file)
+    if version is not None:
+        return version
+    return NoVersionInfo
+
+
+def check_version(module_name, at_least, less_than, version=None, project_name=None):
+    """Check that the version of the given module is at least and less than the given
+    version strings, and raise VersionException if not. Raise VersionException if the
+    module was not found or its version could not be determined. This function uses
+    get_version to determine version numbers without importing modules. In order to do
+    this, project_name must be provided if it differs from module_name. For example,
+    pyserial is imported as 'serial', but the project name, as passed to a 'pip install'
+    command, is 'pyserial'. Therefore to check the version of pyserial, pass in
+    module_name='serial' and project_name='pyserial'. You can also pass in a version
+    string yourself, in which case no inspection of packages will take place.
+    """
+    if version is None:
+        version = get_version(module_name, project_name)
+
+    if version is NotFound:
+        raise VersionException('Module {} not found'.format(module_name))
+
+    if version is NoVersionInfo:
+        raise VersionException(
+            'Could not get version info from module {}'.format(module_name)
+        )
+
+    at_least_version, less_than_version, installed_version = [
+        packaging.version.parse(v) for v in [at_least, less_than, version]
+    ]
+
+    if not at_least_version <= installed_version < less_than_version:
+        msg = (
+            '{module_name} {version} found. '
+            + '{at_least} <= {module_name} < {less_than} required.'
+        )
+        raise VersionException(msg.format(**locals()))
+
+
+if __name__ == '__main__':
+    assert get_version('subprocess') == NoVersionInfo
+    assert get_version('plsgtbg') == NotFound
+    assert type(get_version('labscript_utils')) in [str, bytes]
+    assert type(get_version('numpy')) in [str, bytes]
+    assert type(get_version('serial', 'pyserial')) in [str, bytes]

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