linux安装python3.*，更换Python2.*

下载并解压：Python-3.5.7.tgz

 [root@AH-aQYWTYSJZX01 python3]# ll
 total 20268
 -rw-r----- 1 temp01 temp01 20753760 Jul 11 08:30 Python-3.5.7.tgz
 [root@AH-aQYWTYSJZX01 python3]# tar -zxvf Python-3.5.7.tgz
 ......
 Python-3.5.7/Python/condvar.h
 Python-3.5.7/Python/modsupport.c
 Python-3.5.7/Python/compile.c
 Python-3.5.7/Python/frozenmain.c
 Python-3.5.7/Python/asdl.c
 Python-3.5.7/Python/errors.c
 Python-3.5.7/Python/getplatform.c
 Python-3.5.7/Python/README
 Python-3.5.7/Python/codecs.c
 Python-3.5.7/Python/thread_pthread.h
 Python-3.5.7/Python/Python-ast.c
 Python-3.5.7/Python/ceval.c
 Python-3.5.7/config.sub
 Python-3.5.7/README
 Python-3.5.7/Grammar/
 Python-3.5.7/Grammar/Grammar

 [root@AH-aQYWTYSJZX01 Python-3.5.7]# ./configure --prefix=/usr/local/python3
 ......
 checking for /dev/ptmx... yes
 checking for /dev/ptc... no
 checking for %lld and %llu printf() format support... yes
 checking for %zd printf() format support... yes
 checking for socklen_t... yes
 checking for broken mbstowcs... no
 checking for --with-computed-gotos... no value specified
 checking whether gcc -pthread supports computed gotos... yes
 checking for build directories... done
 checking for -O2... yes
 checking for glibc _FORTIFY_SOURCE/memmove bug... no
 checking for gcc ipa-pure-const bug... no
 checking for stdatomic.h... no
 checking for GCC >= 4.7 __atomic builtins... no
 checking for ensurepip... upgrade
 checking if the dirent structure of a d_type field... yes
 checking for the Linux getrandom() syscall... no
 checking for the getrandom() function... no
 configure: creating ./config.status
 config.status: creating Makefile.pre
 config.status: creating Modules/Setup.config
 config.status: creating Misc/python.pc
 config.status: creating Misc/python-config.sh
 config.status: creating Modules/ld_so_aix
 config.status: creating pyconfig.h
 creating Modules/Setup
 creating Modules/Setup.local
 creating Makefile

 If you want a release build with all stable optimizations active (PGO, etc),
 please run ./configure --enable-optimizations

 [root@AH-aQYWTYSJZX01 Python-3.5.7]# make
 ......
 To find the necessary bits, look in setup.py in detect_modules() for the module's name.

 The following modules found by detect_modules() in setup.py, have been
 built by the Makefile instead, as configured by the Setup files:
 atexit                pwd                   time               

 Failed to build these modules:
 _pickle                                                        

 running build_scripts
 creating build/scripts-3.5
 copying and adjusting /sga/python3/Python-3.5.7/Tools/scripts/pydoc3 -> build/scripts-3.5
 copying and adjusting /sga/python3/Python-3.5.7/Tools/scripts/idle3 -> build/scripts-3.5
 copying and adjusting /sga/python3/Python-3.5.7/Tools/scripts/2to3 -> build/scripts-3.5
 copying and adjusting /sga/python3/Python-3.5.7/Tools/scripts/pyvenv -> build/scripts-3.5
 changing mode of build/scripts-3.5/pydoc3 from 640 to 755
 changing mode of build/scripts-3.5/idle3 from 640 to 755
 changing mode of build/scripts-3.5/2to3 from 640 to 755
 changing mode of build/scripts-3.5/pyvenv from 640 to 755
 renaming build/scripts-3.5/pydoc3 to build/scripts-3.5/pydoc3.5
 renaming build/scripts-3.5/idle3 to build/scripts-3.5/idle3.5
 renaming build/scripts-3.5/2to3 to build/scripts-3.5/2to3-3.5
 renaming build/scripts-3.5/pyvenv to build/scripts-3.5/pyvenv-3.5
 /usr/bin/install -c -m 644 ./Tools/gdb/libpython.py python-gdb.py
 gcc -pthread -c -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes    -Werror=declaration-after-statement   -I. -I./Include    -DPy_BUILD_CORE -o Programs/_testembed.o ./Programs/_testembed.c
 gcc -pthread   -Xlinker -export-dynamic -o Programs/_testembed Programs/_testembed.o libpython3.5m.a -lpthread -ldl  -lutil -lrt   -lm
 # Substitution happens here, as the completely-expanded BINDIR
 # is not available in configure
 sed -e "s,@EXENAME@,/usr/local/python3/bin/python3.5m," < ./Misc/python-config.in >python-config.py
 # Replace makefile compat. variable references with shell script compat. ones;  ->
 LC_ALL=C sed -e 's,\$(\([A-Za-z0-9_]*\)),\$\{\1\},g' < Misc/python-config.sh >python-config
 # On Darwin, always use the python version of the script, the shell
 # version doesn't use the compiler customizations that are provided
 # in python (_osx_support.py).
 if test `uname -s` = Darwin; then \
                 cp python-config.py python-config; \
         fi

 [root@AH-aQYWTYSJZX01 Python-3.5.7]# make install
 ......
 if test "3.5" != "3.5m"; then \
                 rm -f /usr/local/python3/bin/python3.5-config; \
                 (cd /usr/local/python3/bin; ln -s python3.5m-config python3.5-config); \
                 rm -f /usr/local/python3/lib/pkgconfig/python-3.5m.pc; \
                 (cd /usr/local/python3/lib/pkgconfig; ln -s python-3.5.pc python-3.5m.pc); \
         fi
 rm -f /usr/local/python3/bin/python3-config
 (cd /usr/local/python3/bin; ln -s python3.5-config python3-config)
 rm -f /usr/local/python3/lib/pkgconfig/python3.pc
 (cd /usr/local/python3/lib/pkgconfig; ln -s python-3.5.pc python3.pc)
 rm -f /usr/local/python3/bin/idle3
 (cd /usr/local/python3/bin; ln -s idle3.5 idle3)
 rm -f /usr/local/python3/bin/pydoc3
 (cd /usr/local/python3/bin; ln -s pydoc3.5 pydoc3)
 rm -f /usr/local/python3/bin/2to3
 (cd /usr/local/python3/bin; ln -s 2to3-3.5 2to3)
 rm -f /usr/local/python3/bin/pyvenv
 (cd /usr/local/python3/bin; ln -s pyvenv-3.5 pyvenv)
 if test "x" != "x" ; then \
                 rm -f /usr/local/python3/bin/python3-32; \
                 (cd /usr/local/python3/bin; ln -s python3.5-32 python3-32) \
         fi
 rm -f /usr/local/python3/share/man/man1/python3.1
 (cd /usr/local/python3/share/man/man1; ln -s python3.5.1 python3.1)
 if test "xupgrade" != "xno"  ; then \
                 case upgrade in \
                         upgrade) ensurepip="--upgrade" ;; \
                         install|*) ensurepip="" ;; \
                 esac; \
                  ./python -E -m ensurepip \
                         $ensurepip --root=/ ; \
         fi
 Collecting setuptools
 Collecting pip
 Installing collected packages: setuptools, pip
 Successfully installed pip-9.0.1 setuptools-28.8.0

 建立连接(将python3映射到python)
 [root@AH-aQYWTYSJZX01 Python-3.5.7]# mv /usr/bin/python /usr/bin/python.bak
 [root@AH-aQYWTYSJZX01 Python-3.5.7]# ln -s /usr/local/python3/bin/python3 /usr/bin/python
 [root@AH-aQYWTYSJZX01 Python-3.5.7]#python
 或
 [root@AH-aQYWTYSJZX01 Python-3.5.7]# ln -s /usr/local/python3/bin/python3 /usr/bin/python3
 [root@AH-aQYWTYSJZX01 Python-3.5.7]#python3

 将/usr/local/python3/bin加入PATH