Question

我的代码如下：

import sys, importlib

try:
    import pip
except ImportError:
    raise ImportError("Please install pip")

reqs = ["sh", "vcstools"]
for req in reqs:
    sys.stdout.write("checking for %s..." % req)
    try:
        importlib.import_module(req)
        print("found")
    except ImportError:
        print("missing!")
        print("Installing %s..." % req)
        pip.main(['install', '--user', req])
        #importlib.invalidate_caches() python3 only
        # XXX fails
        importlib.import_module(req)
        new_mods = True

    locs = locals()
    locs[req] = sys.modules[req]

print(sh, vcstools)

这是为了在运行时下载（粗略）依赖项并导入它们（是的，我知道，它不尊重版本号，我可以使用virtualenv等等。这些都是单独的问题。）

如果我们运行它（没有安装在〜/ .local中），我们得到以下内容：

checking for sh...missing!
Installing sh...
Downloading/unpacking sh
....
Successfully installed sh
Cleaning up...
Traceback (most recent call last):
  File "test.py", line 20, in <module>
    importlib.import_module(req)
  File "/usr/local/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
ImportError: No module named sh

所以我们看到安装sh模块后，我们无法立即导入它。如果我们重新运行脚本，它将成功，找到前一次运行中安装的sh。

我觉得奇怪的是，我们看不到vcstools的相同行为;它在同一次运行中安装和导入就好了。是什么赋予了？ sh有什么特别之处吗？

这是第二次运行的完整输出。请注意，我们从上次运行中选择sh，然后我们安装vcstools 并导入它而不会出错：

checking for sh...found
checking for vcstools...missing!
Installing vcstools...
Downloading/unpacking vcstools
  Downloading vcstools-0.1.33.tar.gz
  Running setup.py egg_info for package vcstools

Downloading/unpacking pyyaml (from vcstools)
  Downloading PyYAML-3.11.tar.gz (248Kb): 248Kb downloaded
  Running setup.py egg_info for package pyyaml

    skipping 'ext/_yaml.c' Cython extension (up-to-date)
Requirement already satisfied (use --upgrade to upgrade): python-dateutil in /usr/local/lib/python2.7/site-packages (from vcstools)
Installing collected packages: vcstools, pyyaml
  Running setup.py install for vcstools

  Running setup.py install for pyyaml
    checking if libyaml is compilable
    cc -pthread -fno-strict-aliasing -O2 -pipe -DNDEBUG -O2 -pipe -fPIC -fPIC -I/usr/local/include/python2.7 -c build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c -o build/temp.openbsd-5.5-amd64-2.7/check_libyaml.o
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:2:18: error: yaml.h: No such file or directory
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c: In function 'main':
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:5: error: 'yaml_parser_t' undeclared (first use in this function)
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:5: error: (Each undeclared identifier is reported only once
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:5: error: for each function it appears in.)
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:5: error: expected ';' before 'parser'
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:6: error: 'yaml_emitter_t' undeclared (first use in this function)
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:6: error: expected ';' before 'emitter'
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:8: error: 'parser' undeclared (first use in this function)
    build/temp.openbsd-5.5-amd64-2.7/check_libyaml.c:11: error: 'emitter' undeclared (first use in this function)

    libyaml is not found or a compiler error: forcing --without-libyaml
    (if libyaml is installed correctly, you may need to
     specify the option --include-dirs or uncomment and
     modify the parameter include_dirs in setup.cfg)

    skipping 'ext/_yaml.c' Cython extension (up-to-date)
Successfully installed vcstools pyyaml
Cleaning up...
(<module 'sh' (built-in)>, <module 'vcstools' from '/home/edd/.local/lib/python2.7/site-packages/vcstools/__init__.pyc'>)

这是OpenBSD上的Python-2.7。

干杯

编辑：注意new_mods行是多余的。我会把它留在那里，所以输出中的行号不会偏斜。

Answer 1

这可能是您尝试安装到~/.local/...的第一个包 - 这意味着~/.local/...仅使用pip.main(['install', '--user', req])

创建

如果在python启动时不存在〜/ .local，则不会将其添加到sys.path中，并且找不到该模块（即使importlib.invalidate_caches()也没有。）

所以你必须将该路径添加到sys.path中，或者按照this answer中的指示重新加载sys.path，然后它才能工作......

我的解决方案：

import pip
import importlib
import sys

def pip_import(module_name, pip_package=None):
    try:
        mod = importlib.import_module(module_name)
    except ImportError:
        pip.main(['install', '--user', pip_package if pip_package else module_name])

        # If the install path did not exist on start up it has 
        # to be added to sys.path
        if not pip.locations.user_site in sys.path:
            sys.path.append(pip.locations.user_site)

        mod = importlib.import_module(module_name)

    # Add the imported module to the global namespace so it
    # can be used just like `import module`
    globals()[module_name] = mod

导入解释器启动时不可用的Python模块

1 个答案: