遇到的問題：

Traceback (most recent call last):File "D:\miniconda\envs\yolov5\lib\site-packages\git\__init__.py", line 296, in <module>refresh()File "D:\miniconda\envs\yolov5\lib\site-packages\git\__init__.py", line 287, in refreshif not Git.refresh(path=path):File "D:\miniconda\envs\yolov5\lib\site-packages\git\cmd.py", line 877, in refreshraise ImportError(err)
ImportError: GIT_PYTHON_REFRESH environment variable has been set but it has been set with an invalid value.Use only the following values:- quiet|q|silence|s|silent|none|n|0: for no message or exception- warn|w|warning|log|l|1: for a warning message (logging level CRITICAL, displayed by default)- error|e|exception|raise|r|2: for a raised exceptionThe above exception was the direct cause of the following exception:Traceback (most recent call last):File "train.py", line 66, in <module>GIT_INFO = check_git_info()File "D:\miniconda\envs\yolov5\lib\contextlib.py", line 75, in innerreturn func(*args, **kwds)File "C:\Users\莫偉鐸\Desktop\yolov5-7.0\utils\general.py", line 350, in check_git_infoimport gitFile "D:\miniconda\envs\yolov5\lib\site-packages\git\__init__.py", line 298, in <module>raise ImportError("Failed to initialize: {0}".format(_exc)) from _exc
ImportError: Failed to initialize: GIT_PYTHON_REFRESH environment variable has been set but it has been set 
with an invalid value.Use only the following values:- quiet|q|silence|s|silent|none|n|0: for no message or exception- warn|w|warning|log|l|1: for a warning message (logging level CRITICAL, displayed by default)- error|e|exception|raise|r|2: for a raised exception

 File "D:\miniconda\envs\yolov5\lib\site-packages\git\__init__.py", line 296, in <module>refresh()File "D:\miniconda\envs\yolov5\lib\site-packages\git\__init__.py", line 287, in refreshif not Git.refresh(path=path):File "D:\miniconda\envs\yolov5\lib\site-packages\git\cmd.py", line 860, in refreshraise ImportError(err)
ImportError: Bad git executable.
The git executable must be specified in one of the following ways:- be included in your $PATH- be set via $GIT_PYTHON_GIT_EXECUTABLE- explicitly set via git.refresh(<full-path-to-git-executable>)All git commands will error until this is rectified.This initial message can be silenced or aggravated in the future by setting the
$GIT_PYTHON_REFRESH environment variable. Use one of the following values:- quiet|q|silence|s|silent|none|n|0: for no message or exception- warn|w|warning|log|l|1: for a warning message (logging level CRITICAL, displayed by default)- error|e|exception|raise|r|2: for a raised exceptionExample:export GIT_PYTHON_REFRESH=quietThe above exception was the direct cause of the following exception:Traceback (most recent call last):File "train.py", line 66, in <module>GIT_INFO = check_git_info()File "D:\miniconda\envs\yolov5\lib\contextlib.py", line 75, in innerreturn func(*args, **kwds)File "C:\Users\莫偉鐸\Desktop\yolov5-7.0\utils\general.py", line 350, in check_git_infoimport gitFile "D:\miniconda\envs\yolov5\lib\site-packages\git\__init__.py", line 298, in <module>raise ImportError("Failed to initialize: {0}".format(_exc)) from _exc
ImportError: Failed to initialize: Bad git executable.
The git executable must be specified in one of the following ways:- be included in your $PATH- be set via $GIT_PYTHON_GIT_EXECUTABLE- explicitly set via git.refresh(<full-path-to-git-executable>)All git commands will error until this is rectified.This initial message can be silenced or aggravated in the future by setting the
$GIT_PYTHON_REFRESH environment variable. Use one of the following values:- quiet|q|silence|s|silent|none|n|0: for no message or exception- warn|w|warning|log|l|1: for a warning message (logging level CRITICAL, displayed by default)- error|e|exception|raise|r|2: for a raised exceptionExample:export GIT_PYTHON_REFRESH=quiet

原因：

ImportError: Failed to initialize: Bad git executable.
The git executable must be specified in one of the following ways:- be included in your $PATH- be set via $GIT_PYTHON_GIT_EXECUTABLE- explicitly set via git.refresh(<full-path-to-git-executable>)

解決辦法：

下載并安裝 Git：

下面是其官網：https://git-scm.com/download/win

點擊畫圈圈的Click here download，進行下載git

????????安裝完git后，重啟終端（CMD / PowerShell）再運行：輸入git --version出現相應的版本號說明安裝成功。

git --version
# 應輸出：git version 2.x.x

出現下面情況就是安裝成功。

然后輸入指令：

python train.py

就不會報錯了。