opencv-python==4.2.0.34 找不到此版本

使用pip安装requirements.txt里的库时，出现Could not find a version that satisfies the requirement opencv-python==4.2.0.34 (from -r requirements.txt (line 1)) (from versions: )
No matching distribution found for opencv-python==4.2.0.34 (from -r requirements.txt (line 1))
有没有可代替的opencv库。