BackGround

Recently, there is a new 後輩 joined my team who is very good at Python, so i think i got a good chance to start learning python. ^ ^

What i learned

Before:

Only know there is a language called python

After:

But it has many “friends?”

Python2, Python3-> 2 python version

pyenv -> a tool that is used to change which version

pip3, pip -> pip3 is used to download dependency for python2, pip is for python2

virtualenv(knew from my 後輩)->a tool used to make Python env, so i will also use this but not pipenv

pipenv-> pyenv + pip + virtualenv

Let's try something

Before:

➜  ~ which python
/usr/local/bin/python
➜  ~ python -V
Python 2.7.13
➜  ~ python
Python 2.7.13 (default, Jun 22 2017, 17:48:16)
[GCC 4.2.1 Compatible Apple LLVM 8.1.0 (clang-802.0.42)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
➜  ~ python3
zsh: command not found: python3
➜  ~ pip -V
pip 9.0.1 from /usr/local/lib/python2.7/site-packages (python 2.7)
➜  ~ pip3 -V
zsh: command not found: pip3
➜  ~ pyenv -l
zsh: command not found: pyenv
➜  ~ pipenv -V
zsh: command not found: pipenv
➜  ~ virtualenv -V
zsh: command not found: virtualenv

So now i only have python2(pip inside), no python3, pip3, virtualenv, pipenv.

My senior recommend use pyenv to control, so i will install python3

Install pyenv

// insall pyenv
➜  ~ brew install pyenv
➜  ~ pyenv versions (check the python version i can use)
* system (set by /Users/lilinna/.pyenv/version)
// Try install different versions
➜  ~ pyenv install -v 3.5.5
➜  ~ pyenv versions
* system (set by /Users/lilinna/.pyenv/version)
  3.5.5
// I have python3 now! Let's try, need run pyenv rehash when we install or uninstall
// not sure what this doing, google said create shims.(python maintains shims in that directory to match every Python Command across every installed version pf Python)
➜  ~ pyenv rehash
➜  ~ pyenv global 3.5.5
// But
➜  ~ python3 -V
zsh: command not found: python3
➜  ~ python -V
Python 2.7.13
// Need to set PATH !
➜  ~ echo 'export PATH="/Users/lilinna/.pyenv/bin:$PATH"' >> ~/.zshrc
➜  ~ echo -e 'if command -v pyenv 1>/dev/null 2>&1;then\n eval "$(pyenv init -)"\nfi' >> ~/.zshrc
➜  ~ python -V
Python 3.5.5
➜  ~ pip -V
pip 9.0.1 from /Users/lilinna/.pyenv/versions/3.5.5/lib/python3.5/site-packages (python 3.5)
➜  ~ pip3 -V
pip 9.0.1 from /Users/lilinna/.pyenv/versions/3.5.5/lib/python3.5/site-packages (python 3.5)
// But python2 still can be used.
➜  ~ python2 -V
Python 2.7.13
➜  ~ python3 -V
Python 3.5.5
// try install another python2
➜  ~ pyenv install -v 2.7.14
➜  ~ which python2
/usr/local/bin/python2
➜  ~ pyenv rehash
➜  ~ which python2
/Users/lilinna/.pyenv/shims/python2
➜  ~ python2 -V
pyenv: python2: command not found
The `python2' command exists in these Python versions:
  2.7.14
// so python2 not work because i am using 3.5.5 and there is no python2 inside. Need to do
➜  pyenv global 2.7.14
➜  python -V
Python 2.7.14
➜  python2 -V
Python 2.7.14
➜  ~ pip -V
pip 9.0.1 from /Users/lilinna/.pyenv/versions/2.7.14/lib/python2.7/site-packages (python 2.7)

How to use

➜  ~ python
Python 2.7.14 (default, Jan 18 2020, 16:10:59)
[GCC 4.2.1 Compatible Apple LLVM 11.0.0 (clang-1100.0.33.12)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

Lsvirtualenv

Need to try requirements.txt

➜  ~ pip install virtualenv
➜  ~ cd project
➜  project mkdir python_sandbox
➜  python_sandbox virtualenv first
Using base prefix '/Users/lilinna/.pyenv/versions/3.5.5'
➜  ~ virtualenv -p /usr/bin/python2.7 first
Running virtualenv with interpreter /usr/bin/python2.7
➜  ~ source first/bin/activate
(first) ➜  ~ python -V
Python 2.7.10
(first) ➜  ~ deactivate
➜  ~ virtualenv -p /Users/lilinna/.pyenv/shims/python3.5 first
➜  ~ source first/bin/activate
(first) ➜  ~ python -V
Python 3.5.5
(first) ➜  ~ deactivate

// virtualenvwrapper is a helper of virtualenv
➜  ~ pip install virtualenvwrapper
Add "export WORKON_HOME=/Users/lilinna/project/python_sandbox" into zshrc
➜  source ~/.zshrc
➜  source /Users/lilinna/.pyenv/versions/3.5.5/bin/virtualenvwrapper.sh
➜  mkvirtualenv second
(second) ➜  ~ python -V
Python 3.5.5
(second) ➜  deactivate
➜  ~ mkvirtualenv --python=/usr/bin/python2.7 django
(django) ➜  ~ python -V
Python 2.7.10
➜  ~ workon
django
first
second
➜  ~ rmvirtualenv django
Removing django...

pipenv

TBD

pyenv + pip + virtualenv, so more aggregated things ?

pip3 install pipenv
pipenv run XXX

Others

If you are not use pyenv, you can have python2 and python3 at the same time,

and you can change your python to use python2 or python3

vim .bash_profile
//when we run python, should actually run python3, so python is another name of python3 
alias python='python3'   
source .bash_profile

but change version is not easy.

I had some problem like

Failed when i want to install 3.5.0 https://github.com/pyenv/pyenv/issues/950

brew install pyenv-virtualenv
CFLAGS=-I/usr/include/openssl LDFLAGS=-L/usr/lib pyenv install -v 3.5.3
install -v 3.5.0
python3 -V

Practice

I used python to wirte a simple script, to send request by curl http3, to calculate the average response time.

import subprocess
def main():
    http3 = ['curl', '--http3', '-s', 'https://quic.rocks:4433/','-o','output', '-w' ,'%{time_total}']
    http2 = ['curl', '--http2', '-s', 'https://quic.rocks/','-o','output', '-w' ,'%{time_total}']
    http2Result = 0.0
    http3Result = 0.0
    for num in range(0,50):
       out_bytes1 = subprocess.check_output(http2)
       out_text1 = out_bytes1.decode('utf-8')
       http2Result = http2Result + float(out_text1) 
       out_bytes2 = subprocess.check_output(http3)
       out_text2 = out_bytes2.decode('utf-8')
       http3Result = http3Result + float(out_text2)    
    else:
       print ("http3Result:")
       print  (http3Result/50)
       print ("http2Result:")
       print  (http2Result/50)
    exit(0)
if __name__ == '__main__':
    main()
```