psycopg2 导入错误：未定义符号：PQconninfo

Question

无法导入 psycopg2

python控制台输出：

导入 psycopg2

回溯（最近通话最后一个）：文件“”，1号线，在文件“/home/user/.py_virtualenvs/verb_py3/lib/python3.5/site-packages/psycopg2/初始化py”为50行，在

from psycopg2._psycopg import (#noqa ImportError: /home/user/.py_virtualenvs/verb_py3/lib/python3.5/site-packages/psycopg2/_psycopg.cpython-35m-x86_64-linux-gnu.so: 未定义符号: PQconninfo

Answer 1

安装了 psycopg2-binary 包解决了我的问题。

pip install psycopg2-binary

Answer 2

这可能是底层系统中的缺陷问题。共享库可能有多个版本，在运行时您可能无法找到合适的库。解决起来通常很痛苦。由于我看到了同样的问题，我将尝试找出问题所在。这比给出一个固定的解决方案更有用。我仍然需要为自己找到解决方案： 1. 从较新版本构建 libpq 库。2. 找到 psycopg2 在编译时使用的正确 libpq。

进入psycopg2的源目录：

myuid@mycomputer:~/Downloads/psycopg2$ find . -name "*.c" | xargs grep PQconninfo
./psycopg/psycopgmodule.c:    PQconninfoOption *options = NULL;
./psycopg/psycopgmodule.c:    options = PQconninfoParse(Bytes_AS_STRING(dsn), &err);
./psycopg/psycopgmodule.c:            PyErr_SetString(OperationalError, "PQconninfoParse() failed");
./psycopg/psycopgmodule.c:    PQconninfoFree(options);    /* safe on null */
./psycopg/connection_int.c:    PQconninfoOption *connopts, *ptr;
./psycopg/connection_int.c:    connopts = PQconninfoParse(pgdsn, NULL);
./psycopg/connection_int.c:    PQconninfoFree(connopts);
./psycopg/connection_int.c:    PQconninfoOption *options = NULL;
./psycopg/connection_int.c:    if (!(options = PQconninfoParse(dsn, NULL))) {
./psycopg/connection_int.c:    PQconninfoFree(options);
./psycopg/conninfo_type.c:".. seealso:: libpq docs for `PQconninfo()`__ for details.\n"
./psycopg/conninfo_type.c:    PQconninfoOption *options = NULL;
./psycopg/conninfo_type.c:    if (!(options = PQconninfo(self->conn->pgconn))) {
./psycopg/conninfo_type.c:    PQconninfoFree(options);
./psycopg/conninfo_type.c:    PyErr_SetString(NotSupportedError, "PQconninfo not available in libpq < 9.3");
./psycopg/connection_type.c:    PQconninfoOption *options = NULL;
./psycopg/connection_type.c:    if (!(options = PQconninfo(self->pgconn))) {
./psycopg/connection_type.c:    PQconninfoFree(options);
./psycopg/connection_type.c:    PyErr_SetString(NotSupportedError, "PQconninfo not available in libpq < 9.3");
./psycopg/utils.c:/* Make a dict out of PQconninfoOption array */
./psycopg/utils.c:psyco_dict_from_conninfo_options(PQconninfoOption *options, int include_password)
./psycopg/utils.c:    PQconninfoOption *o;

注意：psycopg 作者已经给你答案了：

"PQconninfo not available in libpq < 9.3"

这意味着问题出在运行时较旧的 libpq，您可能使用了较新版本的 libpq，否则 psycopg2 可能无法编译。

顺便说一句： PQconninfo(self->conn->pgconn) 你知道 PQconninfo 是一个 C 函数，它应该在你的 libpq 中

您的错误消息通常会告诉您问题出在哪里，在我的情况下是：

/usr/local/lib/python3.8/site-packages/psycopg2-2.8.5.dev0-py3.8-linux-x86_64.egg/psycopg2
Full error: >>> import psycopg2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.8/site-packages/psycopg2-2.8.5.dev0-py3.8-linux-x86_64.egg/psycopg2/__init__.py", line 50, in <module>
    from psycopg2._psycopg import (                     # noqa
ImportError: /usr/local/lib/python3.8/site-packages/psycopg2-2.8.5.dev0-py3.8-linux-x86_64.egg/psycopg2/_psycopg.cpython-38-x86_64-linux-gnu.so: undefined symbol: PQconninfo

在这里你应该找到一个共享库：

_psycopg.cpython-38-x86_64-linux-gnu.so

看看图书馆：

ldd _psycopg.cpython-38-x86_64-linux-gnu.so
    linux-vdso.so.1 =>  (0x00007ffe985c7000)
    libpq.so.5 => /usr/lib64/libpq.so.5 (0x00007ff922a13000)
    libpthread.so.0 => /usr/lib64/libpthread.so.0 (0x00007ff9227f7000)
    libc.so.6 => /usr/lib64/libc.so.6 (0x00007ff922429000)
    libssl.so.10 => /usr/lib64/libssl.so.10 (0x00007ff9221b7000)
    libcrypto.so.10 => /usr/lib64/libcrypto.so.10 (0x00007ff921d54000)
    libkrb5.so.3 => /usr/lib64/libkrb5.so.3 (0x00007ff921a6b000)
    libcom_err.so.2 => /usr/lib64/libcom_err.so.2 (0x00007ff921867000)
    libgssapi_krb5.so.2 => /usr/lib64/libgssapi_krb5.so.2 (0x00007ff92161a000)
    libldap_r-2.4.so.2 => /usr/lib64/libldap_r-2.4.so.2 (0x00007ff9213bb000)
    /lib64/ld-linux-x86-64.so.2 (0x00007ff922e87000)
    libk5crypto.so.3 => /usr/lib64/libk5crypto.so.3 (0x00007ff921188000)
    libdl.so.2 => /usr/lib64/libdl.so.2 (0x00007ff920f84000)
    libz.so.1 => /usr/lib64/libz.so.1 (0x00007ff920d6e000)
    libkrb5support.so.0 => /usr/lib64/libkrb5support.so.0 (0x00007ff920b5e000)
    libkeyutils.so.1 => /usr/lib64/libkeyutils.so.1 (0x00007ff92095a000)
    libresolv.so.2 => /usr/lib64/libresolv.so.2 (0x00007ff920741000)
    liblber-2.4.so.2 => /usr/lib64/liblber-2.4.so.2 (0x00007ff920532000)
    libsasl2.so.3 => /usr/lib64/libsasl2.so.3 (0x00007ff920315000)
    libssl3.so => /usr/lib64/libssl3.so (0x00007ff9200bc000)
    libsmime3.so => /usr/lib64/libsmime3.so (0x00007ff91fe94000)
    libnss3.so => /usr/lib64/libnss3.so (0x00007ff91fb65000)
    libnssutil3.so => /usr/lib64/libnssutil3.so (0x00007ff91f935000)
    libplds4.so => /usr/lib64/libplds4.so (0x00007ff91f731000)
    libplc4.so => /usr/lib64/libplc4.so (0x00007ff91f52c000)
    libnspr4.so => /usr/lib64/libnspr4.so (0x00007ff91f2ee000)
    libselinux.so.1 => /usr/lib64/libselinux.so.1 (0x00007ff91f0c7000)
    libcrypt.so.1 => /usr/lib64/libcrypt.so.1 (0x00007ff91ee90000)
    librt.so.1 => /usr/lib64/librt.so.1 (0x00007ff91ec88000)
    libpcre.so.1 => /usr/lib64/libpcre.so.1 (0x00007ff91ea26000)
    libfreebl3.so => /usr/lib64/libfreebl3.so (0x00007ff91e823000)

注意这一行：libpq.so.5 => /usr/lib64/libpq.so.5

现在看看这个库，只对PPconninfo感兴趣（它有很多功能和数据）

nm -D /usr/lib64/libpq.so.5 | grep PQconninfo
000000000000cb90 T PQconninfoFree
000000000000df30 T PQconninfoParse

看你没有 PQconninfo 功能。

我相信通过说明如何解决这个问题会更有帮助；这可能会帮助您解决许多类似的问题。

现在我将在我的系统上添加解决方案：

原来我的系统上有多个 libpg。

cd /usr
find . -name "libpq*"
... many others ignored
./pgsql-11/lib/libpq.so

然后将LD_LIBRARY_PATH更新为/usr/pgsql-11/lib:/usr/local/lib64，那么问题就没有了。

python3.8
Python 3.8.1 (default, Jan  7 2020, 15:07:37) 
[GCC 7.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import psycopg2