編譯安裝完Python3之后，使用pip來安裝python庫，發現了如下報錯：
$ pip install numpy pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available. Collecting numpy Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.",)': /simple/numpy/ Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.",)': /simple/numpy/ Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.",)': /simple/numpy/ Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.",)': /simple/numpy/ Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.",)': /simple/numpy/ Could not fetch URL https://pypi.python.org/simple/numpy/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.python.org', port=443): Max retries exceeded with url: /simple/numpy/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.",)) - skipping Could not find a version that satisfies the requirement numpy (from versions: ) No matching distribution found for numpy
網上說了一種解決方案，是在./configure 的時候，加上--with-ssl選項，然后重新編譯安裝，嘗試了下：
$ ./configure --with-ssl ... ... configure: WARNING: unrecognized options: --with-ssl ... ...
出了個警告：不可識別的--with-ssl選項。
./configure --help看了下確實也沒發現這個選項，估計是版本不一致，不大想折騰這個版本問題了，決定換個思路。
嘗試安裝openssl:
$ sudo yum install openssl
安裝成功之后，重新編譯安裝，依舊報這個錯，但是在make的時候有了一些發現：
$ make ... ... Python build finished successfully! The necessary bits to build these optional modules were not found: _bz2 _curses _curses_panel _dbm _gdbm _lzma _sqlite3 _ssl _tkinter readline To find the necessary bits, look in setup.py in detect_modules() for the module's name.
可以看到，這里雖然make成功了，但是報了很多模塊缺失，查看下編譯安裝目錄下的setup.py，搜索_ssl，可以定位到如下代碼：
843 # Detect SSL support for the socket module (via _ssl) 844 search_for_ssl_incs_in = [ 845 '/usr/local/ssl/include', 846 '/usr/contrib/ssl/include/' 847 ] 848 ssl_incs = find_file('openssl/ssl.h', inc_dirs, 849 search_for_ssl_incs_in 850 ) 851 if ssl_incs is not None: 852 krb5_h = find_file('krb5.h', inc_dirs, 853 ['/usr/kerberos/include']) 854 if krb5_h: 855 ssl_incs += krb5_h 856 ssl_libs = find_library_file(self.compiler, 'ssl',lib_dirs, 857 ['/usr/local/ssl/lib', 858 '/usr/contrib/ssl/lib/' 859 ] ) 860 861 if (ssl_incs is not None and 862 ssl_libs is not None): 863 exts.append( Extension('_ssl', ['_ssl.c'], 864 include_dirs = ssl_incs, 865 library_dirs = ssl_libs, 866 libraries = ['ssl', 'crypto'], 867 depends = ['socketmodule.h']), ) 868 else: 869 missing.append('_ssl')
可以看到，setup.py會在'/usr/local/ssl/include', '/usr/contrib/ssl/include/' 這兩個目錄里面搜索'openssl/ssl.h' 這個頭文件，然后會在 '/usr/local/ssl/lib' 和 '/usr/contrib/ssl/lib/' 之中搜索 ssl 的 lib文件，搜索不到，會將_ssl加入missing這個數組里面，然后尋找missing調用的地方：
313 if missing: 314 print() 315 print("Python build finished successfully!") 316 print("The necessary bits to build these optional modules were not " 317 "found:") 318 print_three_column(missing) 319 print("To find the necessary bits, look in setup.py in" 320 " detect_modules() for the module's name.") 321 print()
找到了上面報錯時候的輸出，很明顯，是由於搜索不到ssl.h頭文件或者搜索不到lib文件而導致的報錯，但是我剛剛明明是裝了openssl的啊，為啥還會報找不到呢？手動搜索下：
$ sudo find / -name ssl.h
沒找到ssl.h，折騰了一番之后，找到了如下命令：
$ sudo yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel
可以看到，這個命令安裝的是openssl-devel，與我之前安裝的openssl有所不同，查閱資料之后發現，openssl只包含了可執行部分，openssl-devel才包含了頭文件、頭文件參考、某些庫文件等跟開發相關的東西。所以只安裝openssl是找不到相應的頭文件的，安裝完之后，再次編譯：
$ make clean $ make ... ... Python build finished successfully! The necessary bits to build these optional modules were not found: _dbm _gdbm _lzma To find the necessary bits, look in setup.py in detect_modules() for the module's name.
果然發現，缺失的模塊少了很多。
繼續安裝：
$ sudo make install
安裝完之后，重新執行pip:
$ pip install numpy Collecting numpy Downloading https://files.pythonhosted.org/packages/68/1e/116ad560de97694e2d0c1843a7a0075cc9f49e922454d32f49a80eb6f1f2/numpy-1.14.5-cp36-cp36m-manylinux1_x86_64.whl (12.2MB) 6% |██ | 747kB 10kB/s eta 0:17:52
至此，pip安裝報錯的問題解決。