title: Errrors while installing NLTK
body: <p>while trying to install NLTK by <code>pip install nltk</code> i got the following error </p>
  
  <pre><code>
    ----------------------------------------
    Failed building wheel for nltk
    Running setup.py clean for nltk
    Running setup.py bdist_wheel for regex ... error
    Complete output from command /home/pavan/Desktop/chatbot/myenv/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-s1j858so/regex/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" bdist_wheel -d /tmp/tmp01krw6rjpip-wheel- --python-tag cp35:
    usage: -c [global_opts] cmd1 [cmd1_opts] [cmd2 [cmd2_opts] ...]
       or: -c --help [cmd1 cmd2 ...]
       or: -c --help-commands
       or: -c cmd --help
  
    error: invalid command 'bdist_wheel'
  
    ----------------------------------------
    Failed building wheel for regex
    Running setup.py clean for regex
  Failed to build nltk regex
  Installing collected packages: regex, tqdm, nltk
    Running setup.py install for regex ... error
      Complete output from command /home/pavan/Desktop/chatbot/myenv/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-s1j858so/regex/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-5loncafz-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/pavan/Desktop/chatbot/myenv/include/site/python3.5/regex:
      running install
      running build
      running build_py
      creating build
      creating build/lib.linux-x86_64-3.5
      creating build/lib.linux-x86_64-3.5/regex
      copying regex_3/__init__.py -&gt; build/lib.linux-x86_64-3.5/regex
      copying regex_3/regex.py -&gt; build/lib.linux-x86_64-3.5/regex
      copying regex_3/_regex_core.py -&gt; build/lib.linux-x86_64-3.5/regex
      copying regex_3/test_regex.py -&gt; build/lib.linux-x86_64-3.5/regex
      running build_ext
      building 'regex._regex' extension
      creating build/temp.linux-x86_64-3.5
      creating build/temp.linux-x86_64-3.5/regex_3
      x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -I/home/pavan/Desktop/chatbot/myenv/include -I/usr/include/python3.5m -c regex_3/_regex.c -o build/temp.linux-x86_64-3.5/regex_3/_regex.o
      regex_3/_regex.c:48:20: fatal error: Python.h: No such file or directory
      compilation terminated.
      error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
  
      ----------------------------------------
  Command "/home/pavan/Desktop/chatbot/myenv/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-s1j858so/regex/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-5loncafz-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/pavan/Desktop/chatbot/myenv/include/site/python3.5/regex" failed with error code 1 in /tmp/pip-build-s1j858so/regex/
  You are using pip version 8.1.1, however version 20.1.1 is available.
  You should consider upgrading via the 'pip install --upgrade pip' command.
  </code></pre>
  
  <p>To solve the error <code>error: command 'x86_64-linux-gnu-gcc' failed with exit status 1</code> i tried <code>sudo apt-get install python3-dev</code> as seen in another stackOverflow post but got the error </p>
  
  <pre><code>E: Malformed entry 4 in list file /etc/apt/sources.list.d/additional-repositories.list (Component)
  E: The list of sources could not be read.
  E: Malformed entry 4 in list file /etc/apt/sources.list.d/additional-repositories.list (Component)
  E: The list of sources could not be read.
  </code></pre>
  
  <p>Can someone explain what have gone wrong and what is gcc error?</p>
  
  <p>P.S:- I installed virtualenv by <code>python3 -m venv myenv
  </code></p>