无法导入psycopg2
在python控制台中的输出：
导入psycopg2
回溯（最近通话最近）： 文件“”，第1行，位于
中的文件“ /home/user/.py_virtualenvs/verb_py3/lib/python3.5/site-packages/psycopg2/init.py”，第50行 从psycopg2._psycopg导入（＃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
答案 0 :(得分：3)
这可能是基础系统中的缺陷问题。共享库可能有多个版本，并且在运行时您可能找不到正确的库。解决起来通常很痛苦。由于我遇到了同样的问题，因此我将尝试解决问题。这将比给出固定的解决方案有用。我仍然需要为自己找到解决方案：1.从较新的版本构建libpq库。 2.找到psycopg2在编译时使用的正确的libpq。
转到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作者已经通过行为您提供了答案：
"PQconninfo not available in libpq < 9.3"
这意味着问题是运行时的libpq较旧，您可能使用了libpq的较新版本，否则psycopg2可能无法编译。
根据一行：PQconninfo（self-> conn-> pgconn） 您知道PQconninfo是C函数，应该在您的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
在这里您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)
注意以下行：libpq.so.5 => /usr/lib64/libpq.so.5
现在看看这个库，只对PPconninfo感兴趣（它具有很多功能和数据）
nm -D /usr/lib64/libpq.so.5 | grep PQconninfo
000000000000cb90 T PQconninfoFree
000000000000df30 T PQconninfoParse
看到您没有PQconninfo函数。
我认为通过说明如何解决此问题会更有帮助；这可以帮助您解决许多类似的问题。
现在，我将解决方案添加到我的系统中：
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更新到/ usr / pgsql-11 / lib：/ usr / local / lib64，然后问题就消失了。
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
答案 1 :(得分：1)
使用conda而不是pip重新安装psycopg2解决了该问题。
答案 2 :(得分：0)
安装了psycopg2-binary软件包解决了我的问题。
pip install psycopg2-binary
答案 3 :(得分：0)
就像@Kemin Zhou在一个答案中说的那样，导致此问题的原因之一可能是年龄更大的libpq.so file。
我当前正在使用Cent OS 7，安装的postgresql-lib版本为：
$ yum list installed | grep postgres
Failed to set locale, defaulting to C
postgresql.x86_64 9.2.24-4.el7_8 installed
postgresql-devel.x86_64 9.2.24-4.el7_8 installed
postgresql-libs.x86_64 9.2.24-4.el7_8 installed
我什至无法更新它，因为yum找不到它的更高版本：
$ yum list --showduplicates postgresql
Failed to set locale, defaulting to C
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* epel: mirrors.ircam.fr
Installed Packages
postgresql.x86_64 9.2.24-4.el7_8 installed
Available Packages
postgresql.i686 9.2.24-2.el7 base
postgresql.x86_64 9.2.24-2.el7 base
postgresql.i686 9.2.24-2.el7_7 updates
postgresql.x86_64 9.2.24-2.el7_7 updates
postgresql.i686 9.2.24-4.el7_8 updates
postgresql.x86_64 9.2.24-4.el7_8 updates
This链接帮助了我。
使用该链接，我首先添加了此仓库，其中包含更新的postgresql10-libs：
$ yum install https://download.postgresql.org/pub/repos/yum/10/redhat/rhel-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm
然后我安装了更新的postgresql10-libs
$ yum install postgresql10-libs.x86_64