conda activate

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  • conda 4.12.0
  • macOS 10.15.7

示例为个人 PC 环境下的回显

Conda makes environments first-class citizens, making it easy to create independent environments even for C libraries. Conda is written entirely in Python

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# conda environments:
#
base                     /Users/huangzhesi/miniconda
conda-dev             *  /Users/huangzhesi/miniconda/envs/conda-dev
pandas                   /Users/huangzhesi/miniconda/envs/pandas
pytorch-1.8              /Users/huangzhesi/miniconda/envs/pytorch-1.8
pytorch-dev              /Users/huangzhesi/miniconda/envs/pytorch-dev
tensorflow-1.x           /Users/huangzhesi/miniconda/envs/tensorflow-1.x

今天来探索下我们输入 conda activate conda-dev 命令后，实际上 conda 为了我们做什么

先说结论

  1. 设置了 conda env bin 到环境变量 PATH（替换 old conda env 值，比如 base conda env）
  2. 未修改环境变量 LD_LIBRARY_PATH，原因如下

https://docs.conda.io/projects/conda-build/en/latest/resources/use-shared-libraries.html#shared-libraries-in-macos-and-linux

https://conda.io/projects/conda-build/en/latest/concepts/recipe.html#prefix-replacement

https://github.com/conda/conda/issues/308#issuecomment-36058087

the problem with activate setting LD_LIBRARY_PATH (even when conda packages themselves don’t need it) is that it might break other things on the users system.

源码

https://github.com/conda/conda/tree/4.12.0

conda activate 命令在 conda/activate.py 文件里边实现

调用顺序如下

  1. activate
  2. build_activate
  3. _build_activate_stack

最终返回一个 structure

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return {
    'unset_vars': unset_vars,
    'set_vars': set_vars,
    'export_vars': export_vars,
    'deactivate_scripts': deactivate_scripts,
    'activate_scripts': activate_scripts,
}

可见 conda activate 命令实际上会 unset，set，export vars，以达到激活环境的效果

激活流程

查询 conda env path

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def conda_prefix(self):
    return abspath(sys.prefix)

root_prefix case = conda_prefix = /Users/huangzhesi/miniconda

prefix magic file = {conda_prefix}/conda-meta/history

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# path is the prefix magic file
        if isfile(path):
            try:
                fh = open(path, 'a+')

测试 history file 是否有读写权限

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ls -alh /Users/huangzhesi/miniconda/conda-meta | grep history
-rw-r--r--    1 huangzhesi  staff   8.2K 12 19 21:44 history

(1) 假若 history file 有读写权限，则 context envs dirs 按如下顺序

  1. /Users/huangzhesi/miniconda/envs
  2. ~/.conda/envs

(2) 若 history file 没有读写权限，则 context envs dirs 按如下顺序

  1. ~/.conda/envs
  2. /Users/huangzhesi/miniconda/envs

从 context envs dirs 中查询待激活的 env

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# name is the conda activate {name}
    for envs_dir in envs_dirs:
        if not isdir(envs_dir):
            continue
        prefix = join(envs_dir, name)
        if isdir(prefix):
            return abspath(prefix)

到这里 prefix 就确定了 prefix = locate_prefix_by_name(env_name_or_prefix)

prefix = /Users/huangzhesi/miniconda/envs/conda-dev

  • CONDA_SHLVL=1
  • CONDA_PREFIX=/Users/huangzhesi/miniconda

替换 old_conda_prefix，比如 base conda env

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new_path = self.pathsep_join(
    self._replace_prefix_in_path(old_conda_prefix, prefix))

需要设置的环境变量

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env_vars_to_export = OrderedDict((
    ('path', new_path),
    ('conda_prefix', prefix),
    ('conda_shlvl', new_conda_shlvl),
    ('conda_default_env', conda_default_env),
    ('conda_prompt_modifier', conda_prompt_modifier)))

set ld_library_path inside python

https://stackoverflow.com/questions/6543847/setting-ld-library-path-from-inside-python

https://stackoverflow.com/questions/856116/changing-ld-library-path-at-runtime-for-ctypes

比较 hack，不优雅 …

如果 conda env 中安装的非 conda package，其依赖 shared libraries，没太好办法，手动设置 LD_LIBRARY_PATH 环境变量吧