为什么我不能在Mac OS上点安装nltk?

我正在使用macOS mojave，安装python 2.7并使用 python get-pip.py 安装pip，我已经尝试使用这些命令来安装pip了:

I'm using mac os mojave, install python 2.7 and install pip using python get-pip.py, I already try those command to install pip :

pip install --upgrade pip
pip install nltk

然后尝试

sudo python -m pip install --upgrade nltk

但是也会导致相同的错误，例如此图像

But also result to same error like in this image

或在此处输入文字:

nltk设置命令中的错误:"install_requires"必须为字符串或包含有效项目/版本要求的字符串列表说明符;singledispatch 中的预期版本规范；python_version<3.4"在；python_version<"3.4"

error in nltk setup command: 'install_requires' must be a string or list of strings containing valid project/version requirement specifiers; Expected version spec in singledispatch; python_version < "3.4" at ; python_version < "3.4"

是因为我的python版本(2.7)吗?但是在pip ntlk页面中，它说也支持2.7

Is it because my python version (2.7) ? But in pip ntlk page it says also support 2.7

更新:

pip install nltk 成功:

pip install --upgrade setuptools pip --user