Create venv_management.py, add get_bootstrap_requirements_string() to help in bootstrapping a new venv's torch dependencies based on existing venv

app/venv_management.py

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+import torch
+import torchvision
+import torchaudio
+from dataclasses import dataclass
+
+import importlib
+if importlib.util.find_spec("torch_directml"):
+    from pip._vendor import pkg_resources
+
+
+class VEnvException(Exception):
+    pass
+
+
+@dataclass
+class TorchVersionInfo:
+    name: str = None
+    version: str = None
+    extension: str = None
+    is_nightly: bool = False 
+    is_cpu: bool = False
+    is_cuda: bool = False
+    is_xpu: bool = False
+    is_rocm: bool = False
+    is_directml: bool = False
+
+
+def get_bootstrap_requirements_string():
+    '''
+    Get string to insert into a 'pip install' command to get the same torch dependencies as current venv.
+    '''
+    torch_info = get_torch_info(torch)
+    packages = [torchvision, torchaudio]
+    infos = [torch_info] + [get_torch_info(x) for x in packages]
+    # directml should be first dependency, if exists
+    directml_info = get_torch_directml_info()
+    if directml_info is not None:
+        infos = [directml_info] + infos
+    # create list of strings to combine into install string
+    install_str_list = []
+    for info in infos:
+        info_string = f"{info.name}=={info.version}"
+        if not info.is_cpu and not info.is_directml:
+            info_string = f"{info_string}+{info.extension}"
+        install_str_list.append(info_string)
+    # handle extra_index_url, if needed
+    extra_index_url = get_index_url(torch_info)
+    if extra_index_url:
+        install_str_list.append(extra_index_url)
+    # format nightly install properly
+    if torch_info.is_nightly:
+        install_str_list = ["--pre"] + install_str_list
+
+    install_str  = " ".join(install_str_list)
+    return install_str
+
+def get_index_url(info: TorchVersionInfo=None):
+    '''
+    Get --extra-index-url (or --index-url) for torch install.
+    '''
+    if info is None:
+        info = get_torch_info()
+    # for cpu, don't need any index_url
+    if info.is_cpu and not info.is_nightly:
+        return None
+    # otherwise, format index_url
+    base_url = "https://download.pytorch.org/whl/"
+    if info.is_nightly:
+        base_url = f"--index-url {base_url}nightly/"
+    else:
+        base_url = f"--extra-index-url {base_url}"
+    base_url = f"{base_url}{info.extension}"
+    return base_url
+
+def get_torch_info(package=None):
+    '''
+    Get info about an installed torch-related package.
+    '''
+    if package is None:
+        package = torch
+    info = TorchVersionInfo(name=package.__name__)
+    info.version = package.__version__
+    info.extension = None
+    info.is_nightly = False
+    # get extension, separate from version
+    info.version, info.extension = info.version.split('+', 1)
+    if info.extension.startswith('cpu'):
+        info.is_cpu = True
+    elif info.extension.startswith('cu'):
+        info.is_cuda = True
+    elif info.extension.startswith('rocm'):
+        info.is_rocm = True
+    elif info.extension.startswith('xpu'):
+        info.is_xpu = True
+    # TODO: add checks for some odd pytorch versions, if possible
+
+    # check if nightly install
+    if 'dev' in info.version:
+        info.is_nightly = True
+
+    return info
+
+def get_torch_directml_info():
+    '''
+    Get info specifically about torch-directml package.
+
+    Returns None if torch-directml is not installed.
+    '''
+    # the import string and the pip string are different
+    pip_name = "torch-directml"
+    # if no torch_directml, do nothing
+    if not importlib.util.find_spec("torch_directml"):
+        return None
+    info = TorchVersionInfo(name=pip_name)
+    info.is_directml = True
+    for p in pkg_resources.working_set:
+        if p.project_name.lower() == pip_name:
+            info.version = p.version
+    if p.version is None:
+        return None
+    return info
+
+
+if __name__ == '__main__':
+    print(get_bootstrap_requirements_string())