如何在 ubuntu 20.04 上安装 python3-pip

Question

新手上路，请多包涵

我在 PC 上安装了 Ubuntu 20.04。然后我尝试开始并为 python3 安装 pip。但是似乎没有任何效果。到目前为止，这是我尝试过的：

 sudo apt install python3-pip

这是我得到的错误：

 Reading package lists... Done
Building dependency tree
Reading state information... Done
Package python3-pip is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'python3-pip' has no installation candidate

我尝试了 Carlos Sanchez JR 提出的解决方案： How to install Python package installer PIP on Ubuntu 20.04 Linux

按照上面链接中给出的建议后，我在执行 sudo apt update 时遇到了这个错误：

 Ign:1 cdrom://Ubuntu 20.04 LTS _Focal Fossa_ - Release amd64 (20200423) focal InRelease
Hit:2 cdrom://Ubuntu 20.04 LTS _Focal Fossa_ - Release amd64 (20200423) focal Release
Hit:4 http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:6 http://archive.ubuntu.com/ubuntu focal InRelease
Get:5 http://kali.download/kali kali-rolling InRelease [30.5 kB]
Hit:7 http://archive.ubuntu.com/ubuntu focal-updates InRelease
Err:5 http://kali.download/kali kali-rolling InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ED444FF07D8D0BF6
Get:8 http://kali.cs.nctu.edu.tw/kali kali-rolling InRelease [30.5 kB]
Err:8 http://kali.cs.nctu.edu.tw/kali kali-rolling InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ED444FF07D8D0BF6
Reading package lists... Done
W: GPG error: http://kali.download/kali kali-rolling InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ED444FF07D8D0BF6
E: The repository 'http://http.kali.org/kali kali-rolling InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://kali.cs.nctu.edu.tw/kali kali-rolling InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ED444FF07D8D0BF6
E: The repository 'http://kali.cs.nctu.edu.tw/kali kali-rolling InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

尝试 sudo apt install python3-pip 在这一点上给我同样的 E: Package 'python3-pip' has no installation candidate 和以前一样的错误。尝试 sudo apt-get install python3-pip 时同样如此。

我没有找到解决此问题的其他方法。