python virtual env and venv

pre introduction : stackoverflow what-is-the-difference-between-venv-pyvenv-pyenv-virtualenv-virtualenvwrappe

原先位于 Tips write date: 2021-04-21T00:00:00+08:00

intro

anaconda 和 miniconda 是很常用的多版本 python 的管理器，不过我有几点不满意

过于庞大，不够轻量，即使是 miniconda 好像也有好几百兆
而且 conda channel 什么的整了好久都没整明白，
已经有 pip 了为何还要用 conda install

当然 conda 还提供了一些非 python 的内容，这是 pip 无法做到的，但是这又和 kiss 原则相违背了。

softwares

pyenv: provide python version
venv: provide virtual environment

Working flow example

Configure

install another version of python

2023-06-19 update:

if you want to generate libpython3.so

env CONFIGURE_OPTS="--enable-shared"  pyenv install 3.10

2023-05-26 update:

pyenv install --patch 3.7.9 << alignment.patch

alignment.patch src

--- Include/objimpl.h
+++ Include/objimpl.h
@@ -250,7 +250,7 @@
         union _gc_head *gc_prev;
         Py_ssize_t gc_refs;
     } gc;
-    double dummy;  /* force worst-case alignment */
+    long double dummy;  /* force worst-case alignment */
 } PyGC_Head;

 extern PyGC_Head *_PyGC_generation0;
--- Objects/obmalloc.c
+++ Objects/obmalloc.c
@@ -643,8 +643,8 @@
  *
  * You shouldn't change this unless you know what you are doing.
  */
-#define ALIGNMENT               8               /* must be 2^N */
-#define ALIGNMENT_SHIFT         3
+#define ALIGNMENT               16               /* must be 2^N */
+#define ALIGNMENT_SHIFT         4

 /* Return the number of bytes in size class I, as a uint. */
 #define INDEX2SIZE(I) (((uint)(I) + 1) << ALIGNMENT_SHIFT)

Add that python to $PATH

# default python be python 3.7.9
export PYENV_ROOT="$HOME/.pyenv/versions/3.7.9/"
export PATH="$PYENV_ROOT/bin:$PATH"

Create virtual environment, there will be python command in .venv/3.6/bin, but it is a link to current python.

# create virtual environment
cd ~/.venv
python -m venv 3.7

Active and deactivate it

source ~/.venv/3.7/bin/activate
deactivate

export in the 2nd is no needed this time.

Reuse

Active and deactivate it

source ~/.venv/3.6/bin/activate
deactivate

you can check if it’s enalbed by:

which python3
which pip3

others

Set pyenv as default, not recommend:

# .zshrc
# pyenv
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
if command -v pyenv 1>/dev/null 2>&1; then
  eval "$(pyenv init -)"
fi