python中python2和python3之间怎么转换？ python2和python3的区别，转换及共存
\u5982\u4f55\u628aPython2\u7684\u4ee3\u7801\u8f6c\u6362\u4e3aPython3\u7684\u4ee3\u7801\u53ef\u4ee5\u5229\u7528Python\u5185\u7f6e\u5de5\u51772to3.py\uff0c\u5e2e\u4f60\u81ea\u52a8\u5c06Python2\u7684\u4ee3\u7801\u8f6c\u6362\u4e3aPython3\u7684\u4ee3\u7801\u7684\u3002\u8fd9\u4e2a\u811a\u672c\u7684\u4f4d\u7f6e\u4f4d\u5728Python\u5b89\u88c5\u7684\u6839\u76ee\u5f55\Python27\Tools\Scripts\2to3.py\u3002
\u6bd4\u5982\u6211\u624b\u4e0a\u6709\u4e2aPython 2.x\u7684python\u811a\u672c\uff1aD:\tmp\transform.py
\u53ef\u4ee5\u901a\u8fc7\u6253\u5f00\u547d\u4ee4\u63d0\u793a\u7b26\uff0c\u5b9a\u4f4d\u81f3\u8be5\u8981\u8f6c\u6362\u7684\u811a\u672c\u76ee\u5f55\u4e0b\uff0c\u7136\u540e\u8fd0\u884c
2to3.py -w transform.py
\u5982\u679c\u4e0a\u8ff0\u4e0d\u52a0-w\u53c2\u6570\uff0c\u5219\u9ed8\u8ba4\u53ea\u662f\u628a\u8f6c\u6362\u8fc7\u7a0b\u6240\u5bf9\u5e94\u7684diff\u5185\u5bb9\u6253\u5370\u8f93\u51fa\u5230\u5f53\u524d\u7a97\u53e3\u800c\u5df2\u3002\u52a0\u4e86-w\uff0c\u5c31\u662f\u628a\u6539\u52a8\u5185\u5bb9\uff0c\u5199\u56de\u5230\u539f\u5148\u7684\u6587\u4ef6\u4e86\u3002
python2\u548cpython3\u7684\u533a\u522b
1.\u6027\u80fd
Py3.0\u8fd0\u884c pystone benchmark\u7684\u901f\u5ea6\u6bd4Py2.5\u616230%\u3002Guido\u8ba4\u4e3aPy3.0\u6709\u6781\u5927\u7684\u4f18\u5316\u7a7a\u95f4\uff0c\u5728\u5b57\u7b26\u4e32\u548c\u6574\u5f62\u64cd\u4f5c\u4e0a\u53ef\u4ee5\u53d6\u5f97\u5f88\u597d\u7684\u4f18\u5316\u7ed3\u679c\u3002
Py3.1\u6027\u80fd\u6bd4Py2.5\u616215%\uff0c\u8fd8\u6709\u5f88\u5927\u7684\u63d0\u5347\u7a7a\u95f4\u3002
2.\u7f16\u7801
Py3.X\u6e90\u7801\u6587\u4ef6\u9ed8\u8ba4\u4f7f\u7528utf-8\u7f16\u7801\uff0c\u8fd9\u5c31\u4f7f\u5f97\u4ee5\u4e0b\u4ee3\u7801\u662f\u5408\u6cd5\u7684\uff1a >>> \u4e2d\u56fd = 'china' >>>print(\u4e2d\u56fd) china
3. \u8bed\u6cd5
1\uff09\u53bb\u9664\u4e86\uff0c\u5168\u90e8\u6539\u7528!=
\u5728Python 2\u91cc\uff0c\u4e3a\u4e86\u5f97\u5230\u4e00\u4e2a\u4efb\u610f\u5bf9\u8c61\u7684\u5b57\u7b26\u4e32\u8868\u793a\uff0c\u6709\u4e00\u79cd\u628a\u5bf9\u8c61\u5305\u88c5\u5728\u53cd\u5f15\u53f7\u91cc(\u6bd4\u5982`x`)\u7684\u7279\u6b8a\u8bed\u6cd5\u3002\u5728Python 3\u91cc\uff0c\u8fd9\u79cd\u80fd\u529b\u4ecd\u7136\u5b58\u5728\uff0c\u4f46\u662f\u4f60\u4e0d\u80fd\u518d\u4f7f\u7528\u53cd\u5f15\u53f7\u83b7\u5f97\u8fd9\u79cd\u5b57\u7b26\u4e32\u8868\u793a\u4e86\u3002\u4f60\u9700\u8981\u4f7f\u7528\u5168\u5c40\u51fd\u6570repr()\u3002
Notes
Python 2
Python 3
\u2460
`x` repr(x)
\u2461
`'PapayaWhip' + `2`` repr('PapayaWhip'+ repr(2))
Note:x\u53ef\u4ee5\u662f\u4efb\u4f55\u4e1c\u897f \u2014 \u4e00\u4e2a\u7c7b\uff0c\u51fd\u6570\uff0c\u6a21\u5757\uff0c\u57fa\u672c\u6570\u636e\u7c7b\u578b\uff0c\u7b49\u7b49\u3002repr()\u51fd\u6570\u53ef\u4ee5\u4f7f\u7528\u4efb\u4f55\u7c7b\u578b\u7684\u53c2\u6570\u3002
2\uff09\u53bb\u9664``\uff0c\u5168\u90e8\u6539\u7528repr()
3\uff09\u5173\u952e\u8bcd\u52a0\u5165as \u548cwith\uff0c\u8fd8\u6709True,False,None
4\uff09\u6574\u578b\u9664\u6cd5\u8fd4\u56de\u6d6e\u70b9\u6570\uff0c\u8981\u5f97\u5230\u6574\u578b\u7ed3\u679c\uff0c\u8bf7\u4f7f\u7528//
\u7531\u4e8e\u4eba\u4eec\u5e38\u5e38\u4f1a\u5ffd\u89c6Python 3\u5728\u6574\u6570\u9664\u6cd5\u4e0a\u7684\u6539\u52a8\uff08\u5199\u9519\u4e86\u4e5f\u4e0d\u4f1a\u89e6\u53d1Syntax Error\uff09\uff0c\u6240\u4ee5\u5728\u79fb\u690d\u4ee3\u7801\u6216\u5728Python 2\u4e2d\u6267\u884cPython 3\u7684\u4ee3\u7801\u65f6\uff0c\u9700\u8981\u7279\u522b\u6ce8\u610f\u8fd9\u4e2a\u6539\u52a8\u3002
\u6240\u4ee5\uff0c\u6211\u8fd8\u662f\u4f1a\u5728Python 3\u7684\u811a\u672c\u4e2d\u5c1d\u8bd5\u7528float(3)/2\u6216 3/2.0\u4ee3\u66ff3/2\uff0c\u4ee5\u6b64\u6765\u907f\u514d\u4ee3\u7801\u5728Python 2\u73af\u5883\u4e0b\u53ef\u80fd\u5bfc\u81f4\u7684\u9519\u8bef\uff08\u6216\u4e0e\u4e4b\u76f8\u53cd\uff0c\u5728Python 2\u811a\u672c\u4e2d\u7528from __future__ import division\u6765\u4f7f\u7528Python 3\u7684\u9664\u6cd5\uff09\u3002
Python 2
print '3 / 2 =', 3 / 2 print '3 // 2 =', 3 // 2 print '3 / 2.0 =', 3 / 2.0 print '3 // 2.0 =', 3 // 2.0 3 / 2 = 1 3 // 2 = 1 3 / 2.0 = 1.5 3 // 2.0 = 1.0
\u9ed8\u8ba4\uff0c\u5982\u679c\u4e24\u4e2a\u64cd\u4f5c\u6570\u90fd\u662f\u6574\u6570\uff0cPython 2 \u81ea\u52a8\u6267\u884c\u6574\u578b\u8ba1\u7b97\u3002
Python 3
print('3 / 2 =', 3 / 2) print('3 // 2 =', 3 // 2) print('3 / 2.0 =', 3 / 2.0) print('3 // 2.0 =', 3 // 2.0) 3 / 2 = 1.5 3 // 2 = 1 3 / 2.0 = 1.5 3 // 2.0 = 1.0
Note: \u9700\u8981\u6ce8\u610f\u7684\u662f\u201c\u53cc\u5212\u7ebf\u201d\uff08//\uff09\u64cd\u4f5c\u7b26\u5c06\u4e00\u76f4\u6267\u884c\u6574\u9664\uff0c\u800c\u4e0d\u7ba1\u64cd\u4f5c\u6570\u7684\u7c7b\u578b\uff0c\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48 5.0//2.0 \u503c\u4e3a 2.0\u3002Python 3 \u4e2d\uff0c/ \u64cd\u4f5c\u7b26\u662f\u505a\u6d6e\u70b9\u9664\u6cd5\uff0c\u800c // \u662f\u505a\u6574\u9664\uff08\u5373\u5546\u6ca1\u6709\u4f59\u6570\uff0c\u6bd4\u5982 10 // 3 \u5176\u7ed3\u679c\u5c31\u4e3a 3\uff0c\u4f59\u6570\u4f1a\u88ab\u622a\u9664\u6389\uff0c\u800c (-7) // 3 \u7684\u7ed3\u679c\u5374\u662f -3\u3002\u8fd9\u4e2a\u7b97\u6cd5\u4e0e\u5176\u5b83\u5f88\u591a\u7f16\u7a0b\u8bed\u8a00\u4e0d\u4e00\u6837\uff0c\u9700\u8981\u6ce8\u610f\uff0c\u5b83\u4eec\u7684\u6574\u9664\u8fd0\u7b97\u4f1a\u54110\u7684\u65b9\u5411\u53d6\u503c\u3002\u800c\u5728 Python 2 \u4e2d\uff0c/ \u5c31\u662f\u6574\u9664\uff0c\u5373\u548c Python 3 \u4e2d\u7684 // \u64cd\u4f5c\u7b26\u4e00\u6837\u3002
5\uff09\u52a0\u5165nonlocal\u8bed\u53e5\u3002\u4f7f\u7528noclocal x\u53ef\u4ee5\u76f4\u63a5\u6307\u6d3e\u5916\u56f4\uff08\u975e\u5168\u5c40\uff09\u53d8\u91cf
6\uff09print
\u53bb\u9664print\u8bed\u53e5\uff0c\u52a0\u5165print()\u51fd\u6570\u5b9e\u73b0\u76f8\u540c\u7684\u529f\u80fd\u3002\u540c\u6837\u7684\u8fd8\u6709 exec\u8bed\u53e5\uff0c\u5df2\u7ecf\u6539\u4e3aexec()\u51fd\u6570
\u5728Python 2\u91cc\uff0cprint\u662f\u4e00\u4e2a\u8bed\u53e5\u3002\u65e0\u8bba\u4f60\u60f3\u8f93\u51fa\u4ec0\u4e48\uff0c\u53ea\u8981\u5c06\u5b83\u4eec\u653e\u5728print\u5173\u952e\u5b57\u540e\u8fb9\u5c31\u53ef\u4ee5\u3002
Python 3\u91cc\uff0cprint()\u662f\u4e00\u4e2a\u51fd\u6570\u3002\u5c31\u50cf\u5176\u4ed6\u7684\u51fd\u6570\u4e00\u6837\uff0cprint()\u9700\u8981\u4f60\u5c06\u60f3\u8981\u8f93\u51fa\u7684\u4e1c\u897f\u4f5c\u4e3a\u53c2\u6570\u4f20\u7ed9\u5b83\u3002
\u4f8b\u5982\uff1a 2.X: print "The answer is", 2*2 3.X: print("The answer is", 2*2) 2.X: print x, # \u4f7f\u7528\u9017\u53f7\u7ed3\u5c3e\u7981\u6b62\u6362\u884c 3.X: print(x, end=" ") # \u4f7f\u7528\u7a7a\u683c\u4ee3\u66ff\u6362\u884c
\u5728Python 2\u91cc\uff0c\u5982\u679c\u4f60\u4f7f\u7528\u4e00\u4e2a\u9017\u53f7(,)\u4f5c\u4e3aprint\u8bed\u53e5\u7684\u7ed3\u5c3e\uff0c\u5b83\u5c06\u4f1a\u7528\u7a7a\u683c\u5206\u9694\u8f93\u51fa\u7684\u7ed3\u679c\uff0c\u7136\u540e\u5728\u8f93\u51fa\u4e00\u4e2a\u5c3e\u968f\u7684\u7a7a\u683c(trailing space)\uff0c\u800c\u4e0d\u8f93\u51fa\u56de\u8f66(carriage return)\u3002\u5728Python 3\u91cc\uff0c\u901a\u8fc7\u628aend=' '\u4f5c\u4e3a\u4e00\u4e2a\u5173\u952e\u5b57\u53c2\u6570\u4f20\u7ed9print()\u53ef\u4ee5\u5b9e\u73b0\u540c\u6837\u7684\u6548\u679c\u3002\u53c2\u6570end\u7684\u9ed8\u8ba4\u503c\u4e3a'\n'\uff0c\u6240\u4ee5\u901a\u8fc7\u91cd\u65b0\u6307\u5b9aend\u53c2\u6570\u7684\u503c\uff0c\u53ef\u4ee5\u53d6\u6d88\u5728\u672b\u5c3e\u8f93\u51fa\u56de\u8f66\u7b26\u30022.X: print # \u8f93\u51fa\u65b0\u884c 3.X: print() # \u8f93\u51fa\u65b0\u884c 2.X: print >>sys.stderr, "fatal error" 3.X: print("fatal error", file=sys.stderr)
\u5728Python 2\u91cc\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7\u4f7f\u7528>>pipe_name\u8bed\u6cd5\uff0c\u628a\u8f93\u51fa\u91cd\u5b9a\u5411\u5230\u4e00\u4e2a\u7ba1\u9053\uff0c\u6bd4\u5982sys.stderr\u3002\u5728Python 3\u91cc\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7\u5c06\u7ba1\u9053\u4f5c\u4e3a\u5173\u952e\u5b57\u53c2\u6570file\u7684\u503c\u4f20\u9012\u7ed9print()\u6765\u5b8c\u6210\u540c\u6837\u7684\u529f\u80fd\u3002\u53c2\u6570file\u7684\u9ed8\u8ba4\u503c\u4e3astd.stdout\uff0c\u6240\u4ee5\u91cd\u65b0\u6307\u5b9a\u5b83\u7684\u503c\u5c06\u4f1a\u4f7fprint()\u8f93\u51fa\u5230\u4e00\u4e2a\u53e6\u5916\u4e00\u4e2a\u7ba1\u9053\u30022.X: print (x, y) # \u8f93\u51farepr((x, y)) 3.X: print((x, y)) # \u4e0d\u540c\u4e8eprint(x, y)!
exec\u8bed\u53e5
exec()\u51fd\u6570\u4f7f\u7528\u4e00\u4e2a\u5305\u542b\u4efb\u610fPython\u4ee3\u7801\u7684\u5b57\u7b26\u4e32\u4f5c\u4e3a\u53c2\u6570\uff0c\u7136\u540e\u5c31\u50cf\u6267\u884c\u8bed\u53e5\u6216\u8005\u8868\u8fbe\u5f0f\u4e00\u6837\u6267\u884c\u5b83\u3002exec()\u8ddfeval()\u662f\u76f8\u4f3c\u7684\uff0c\u4f46\u662fexec()\u66f4\u52a0\u5f3a\u5927\u5e76\u66f4\u5177\u6709\u6280\u5de7\u6027\u3002eval()\u51fd\u6570\u53ea\u80fd\u6267\u884c\u5355\u72ec\u4e00\u6761\u8868\u8fbe\u5f0f\uff0c\u4f46\u662fexec()\u80fd\u591f\u6267\u884c\u591a\u6761\u8bed\u53e5\uff0c\u5bfc\u5165(import)\uff0c\u51fd\u6570\u58f0\u660e \u2014 \u5b9e\u9645\u4e0a\u6574\u4e2aPython\u7a0b\u5e8f\u7684\u5b57\u7b26\u4e32\u8868\u793a\u4e5f\u53ef\u4ee5\u3002
Notes
Python 2
Python 3
\u2460
exec codeString exec(codeString)
\u2461
exec codeString in a_global_namespace exec(codeString, a_global_namespace)
\u2462
exec codeString in a_global_namespace, a_local_namespace exec(codeString, a_global_namespace, a_local_namespace)
\u5728\u6700\u7b80\u5355\u7684\u5f62\u5f0f\u4e0b\uff0c\u56e0\u4e3aexec()\u73b0\u5728\u662f\u4e00\u4e2a\u51fd\u6570\uff0c\u800c\u4e0d\u662f\u8bed\u53e5\uff0c2to3\u4f1a\u628a\u8fd9\u4e2a\u5b57\u7b26\u4e32\u5f62\u5f0f\u7684\u4ee3\u7801\u7528\u62ec\u53f7\u56f4\u8d77\u6765\u3002
Python 2\u91cc\u7684exec\u8bed\u53e5\u53ef\u4ee5\u6307\u5b9a\u540d\u5b57\u7a7a\u95f4\uff0c\u4ee3\u7801\u5c06\u5728\u8fd9\u4e2a\u7531\u5168\u5c40\u5bf9\u8c61\u7ec4\u6210\u7684\u79c1\u6709\u7a7a\u95f4\u91cc\u6267\u884c\u3002Python 3\u4e5f\u6709\u8fd9\u6837\u7684\u529f\u80fd\uff1b\u4f60\u53ea\u9700\u8981\u628a\u8fd9\u4e2a\u540d\u5b57\u7a7a\u95f4\u4f5c\u4e3a\u7b2c\u4e8c\u4e2a\u53c2\u6570\u4f20\u9012\u7ed9exec()\u51fd\u6570\u3002
\u66f4\u52a0\u795e\u5947\u7684\u662f\uff0cPython 2\u91cc\u7684exec\u8bed\u53e5\u8fd8\u53ef\u4ee5\u6307\u5b9a\u4e00\u4e2a\u672c\u5730\u540d\u5b57\u7a7a\u95f4(\u6bd4\u5982\u4e00\u4e2a\u51fd\u6570\u91cc\u58f0\u660e\u7684\u53d8\u91cf)\u3002\u5728Python 3\u91cc\uff0cexec()\u51fd\u6570\u4e5f\u6709\u8fd9\u6837\u7684\u529f\u80fd\u3002
execfile\u8bed\u53e5
\u5c31\u50cf\u4ee5\u524d\u7684exec\u8bed\u53e5\uff0cPython 2\u91cc\u7684execfile\u8bed\u53e5\u4e5f\u53ef\u4ee5\u50cf\u6267\u884cPython\u4ee3\u7801\u90a3\u6837\u4f7f\u7528\u5b57\u7b26\u4e32\u3002\u4e0d\u540c\u7684\u662fexec\u4f7f\u7528\u5b57\u7b26\u4e32\uff0c\u800cexecfile\u5219\u4f7f\u7528\u6587\u4ef6\u3002\u5728Python 3\u91cc\uff0cexecfile\u8bed\u53e5\u5df2\u7ecf\u88ab\u53bb\u6389\u4e86\u3002\u5982\u679c\u4f60\u771f\u7684\u60f3\u8981\u6267\u884c\u4e00\u4e2a\u6587\u4ef6\u91cc\u7684Python\u4ee3\u7801(\u4f46\u662f\u4f60\u4e0d\u60f3\u5bfc\u5165\u5b83)\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7\u6253\u5f00\u8fd9\u4e2a\u6587\u4ef6\uff0c\u8bfb\u53d6\u5b83\u7684\u5185\u5bb9\uff0c\u7136\u540e\u8c03\u7528compile()\u5168\u5c40\u51fd\u6570\u5f3a\u5236Python\u89e3\u91ca\u5668\u7f16\u8bd1\u4ee3\u7801\uff0c\u7136\u540e\u8c03\u7528\u65b0\u7684exec()\u51fd\u6570\u3002
Notes
Python 2
Python 3
execfile('a_filename') exec(compile(open('a_filename').read(),'a_filename','exec'))
7\uff09\u8f93\u5165\u51fd\u6570\u6539\u53d8\u4e86\uff0c\u5220\u9664\u4e86raw_input\uff0c\u7528input\u4ee3\u66ff\uff1a Python 2\u6709\u4e24\u4e2a\u5168\u5c40\u51fd\u6570\uff0c\u7528\u6765\u5728\u547d\u4ee4\u884c\u8bf7\u6c42\u7528\u6237\u8f93\u5165\u3002\u7b2c\u4e00\u4e2a\u53eb\u505ainput()\uff0c\u5b83\u7b49\u5f85\u7528\u6237\u8f93\u5165\u4e00\u4e2aPython\u8868\u8fbe\u5f0f(\u7136\u540e\u8fd4\u56de\u7ed3\u679c)\u3002\u7b2c\u4e8c\u4e2a\u53eb\u505araw_input()\uff0c\u7528\u6237\u8f93\u5165\u4ec0\u4e48\u5b83\u5c31\u8fd4\u56de\u4ec0\u4e48\u3002\u8fd9\u8ba9\u521d\u5b66\u8005\u975e\u5e38\u56f0\u60d1\uff0c\u5e76\u4e14\u8fd9\u88ab\u5e7f\u6cdb\u5730\u770b\u4f5c\u662fPython\u8bed\u8a00\u7684\u4e00\u4e2a\u201c\u8089\u8d58\u201d(wart)\u3002Python 3\u901a\u8fc7\u91cd\u547d\u540draw_input()\u4e3ainput()\uff0c\u4ece\u800c\u5207\u6389\u4e86\u8fd9\u4e2a\u8089\u8d58\uff0c\u6240\u4ee5\u73b0\u5728\u7684input()\u5c31\u50cf\u6bcf\u4e2a\u4eba\u6700\u521d\u671f\u5f85\u7684\u90a3\u6837\u5de5\u4f5c\u30022.X:guess = int(raw_input('Enter an integer : ')) # \u8bfb\u53d6\u952e\u76d8\u8f93\u5165\u7684\u65b9\u6cd5 3.X:guess = int(input('Enter an integer : '))
Note:\u5982\u679c\u4f60\u771f\u7684\u60f3\u8981\u8bf7\u6c42\u7528\u6237\u8f93\u5165\u4e00\u4e2aPython\u8868\u8fbe\u5f0f\uff0c\u8ba1\u7b97\u7ed3\u679c\uff0c\u53ef\u4ee5\u901a\u8fc7\u8c03\u7528input()\u51fd\u6570\u7136\u540e\u628a\u8fd4\u56de\u503c\u4f20\u9012\u7ed9eval()\u3002
I/O\u65b9\u6cd5xreadlines()
\u5728Python 2\u91cc\uff0c\u6587\u4ef6\u5bf9\u8c61\u6709\u4e00\u4e2axreadlines()\u65b9\u6cd5\uff0c\u5b83\u8fd4\u56de\u4e00\u4e2a\u8fed\u4ee3\u5668\uff0c\u4e00\u6b21\u8bfb\u53d6\u6587\u4ef6\u7684\u4e00\u884c\u3002\u8fd9\u5728for\u5faa\u73af\u4e2d\u5c24\u5176\u6709\u7528\u3002\u4e8b\u5b9e\u4e0a\uff0c\u540e\u6765\u7684Python 2\u7248\u672c\u7ed9\u6587\u4ef6\u5bf9\u8c61\u672c\u8eab\u6dfb\u52a0\u4e86\u8fd9\u6837\u7684\u529f\u80fd\u3002
\u5728Python 3\u91cc\uff0cxreadlines()\u65b9\u6cd5\u4e0d\u518d\u53ef\u7528\u4e86\u30022to3\u53ef\u4ee5\u89e3\u51b3\u7b80\u5355\u7684\u60c5\u51b5\uff0c\u4f46\u662f\u4e00\u4e9b\u8fb9\u7f18\u6848\u4f8b\u5219\u9700\u8981\u4eba\u5de5\u4ecb\u5165\u3002
Notes
Python 2
Python 3
\u2460
for line in a_file.xreadlines(): for line in a_file:
\u2461
for line in a_file.xreadlines(5): no change (broken)
\u5982\u679c\u4f60\u4ee5\u524d\u8c03\u7528\u6ca1\u6709\u53c2\u6570\u7684xreadlines()\uff0c2to3\u4f1a\u628a\u5b83\u8f6c\u6362\u6210\u6587\u4ef6\u5bf9\u8c61\u672c\u8eab\u3002\u5728Python 3\u91cc\uff0c\u8fd9\u79cd\u8f6c\u6362\u540e\u7684\u4ee3\u7801\u53ef\u4ee5\u5b8c\u6210\u524d\u540c\u6837\u7684\u5de5\u4f5c\uff1a\u4e00\u6b21\u8bfb\u53d6\u6587\u4ef6\u7684\u4e00\u884c\uff0c\u7136\u540e\u6267\u884cfor\u5faa\u73af\u7684\u5faa\u73af\u4f53\u3002
\u5982\u679c\u4f60\u4ee5\u524d\u4f7f\u7528\u4e00\u4e2a\u53c2\u6570(\u6bcf\u6b21\u8bfb\u53d6\u7684\u884c\u6570)\u8c03\u7528xreadlines()\uff0c2to3\u4e0d\u80fd\u4e3a\u4f60\u5b8c\u6210\u4ecePython 2\u5230Python 3\u7684\u8f6c\u6362\uff0c\u4f60\u7684\u4ee3\u7801\u4f1a\u4ee5\u8fd9\u6837\u7684\u65b9\u5f0f\u5931\u8d25\uff1aAttributeError: '_io.TextIOWrapper' object has no attribute 'xreadlines'\u3002\u4f60\u53ef\u4ee5\u624b\u5de5\u7684\u628axreadlines()\u6539\u6210readlines()\u4ee5\u4f7f\u4ee3\u7801\u80fd\u5728Python 3\u4e0b\u5de5\u4f5c\u3002(readline()\u65b9\u6cd5\u5728Python 3\u91cc\u8fd4\u56de\u8fed\u4ee3\u5668\uff0c\u6240\u4ee5\u5b83\u8ddfPython 2\u91cc\u7684xreadlines()\u6548\u7387\u662f\u4e0d\u76f8\u4e0a\u4e0b\u7684\u3002)
8\uff09\u6539\u53d8\u4e86\u987a\u5e8f\u64cd\u4f5c\u7b26\u7684\u884c\u4e3a\uff0c\u4f8b\u5982x<y\uff0c\u5f53x\u548cy\u7c7b\u578b\u4e0d\u5339\u914d\u65f6\u629b\u51faTypeError\u800c\u4e0d\u662f\u8fd4\u56de\u968f\u5373\u7684 bool\u503c
9\uff09\u53bb\u9664\u5143\u7ec4\u53c2\u6570\u89e3\u5305\u3002\u4e0d\u80fddef(a, (b, c)):pass\u8fd9\u6837\u5b9a\u4e49\u51fd\u6570\u4e86
10\uff09\u65b0\u5f0f\u76848\u8fdb\u5236\u5b57\u53d8\u91cf\uff0c\u76f8\u5e94\u5730\u4fee\u6539\u4e86oct()\u51fd\u6570\u30022.X\u7684\u65b9\u5f0f\u5982\u4e0b\uff1a >>> 0666 438 >>> oct(438) '0666'
3.X\u8fd9\u6837\uff1a >>> 0666 SyntaxError: invalid token (, line 1) >>> 0o666 438 >>> oct(438) '0o666'
11\uff09\u589e\u52a0\u4e86 2\u8fdb\u5236\u5b57\u9762\u91cf\u548cbin()\u51fd\u6570 >>> bin(438) '0b110110110' >>> _438 = '0b110110110' >>> _438 '0b110110110'
12\uff09\u6269\u5c55\u7684\u53ef\u8fed\u4ee3\u89e3\u5305\u3002\u5728Py3.X \u91cc\uff0ca, b, *rest = seq\u548c *rest, a = seq\u90fd\u662f\u5408\u6cd5\u7684\uff0c\u53ea\u8981\u6c42\u4e24\u70b9\uff1arest\u662flist\u5bf9\u8c61\u548cseq\u662f\u53ef\u8fed\u4ee3\u7684\u3002
13\uff09\u65b0\u7684super()\uff0c\u53ef\u4ee5\u4e0d\u518d\u7ed9super()\u4f20\u53c2\u6570\uff0c>>> class C(object): def __init__(self, a): print('C', a) >>> class D(C): def __init(self, a): super().__init__(a) # \u65e0\u53c2\u6570\u8c03\u7528super() >>> D(8) C 8
14\uff09\u652f\u6301class decorator\u3002\u7528\u6cd5\u4e0e\u51fd\u6570decorator\u4e00\u6837\uff1a>>> def foo(cls_a): def print_func(self): print('Hello, world!') cls_a.print = print_func return cls_a >>> @foo class C(object): pass >>> C().print() Hello, world!
class decorator\u53ef\u4ee5\u7528\u6765\u73a9\u73a9\u72f8\u732b\u6362\u592a\u5b50\u7684\u5927\u628a\u620f\u3002\u66f4\u591a\u8bf7\u53c2\u9605PEP 3129
4. \u5b57\u7b26\u4e32\u548c\u5b57\u8282\u4e32
Python 2\u6709\u4e24\u79cd\u5b57\u7b26\u4e32\u7c7b\u578b\uff1aUnicode\u5b57\u7b26\u4e32\u548c\u975eUnicode\u5b57\u7b26\u4e32\u3002Python 2\u6709\u57fa\u4e8eASCII\u7684str()\u7c7b\u578b\uff0c\u5176\u53ef\u901a\u8fc7\u5355\u72ec\u7684unicode()\u51fd\u6570\u8f6c\u6210unicode\u7c7b\u578b\uff0c\u4f46\u6ca1\u6709byte\u7c7b\u578b\u3002
\u800c\u5728Python 3\u4e2d\uff0c\u7ec8\u4e8e\u6709\u4e86Unicode\uff08utf-8\uff09\u5b57\u7b26\u4e32\uff0c\u4ee5\u53ca\u4e24\u4e2a\u5b57\u8282\u7c7b\uff1abytes\u548cbytearrays\u3002Python 3\u53ea\u6709\u4e00\u79cd\u7c7b\u578b\uff1aUnicode\u5b57\u7b26\u4e32(Unicode strings)\u3002\u53ea\u6709str\u4e00\u79cd\u7c7b\u578b\uff0c\u4f46\u5b83\u8ddf2.x\u7248\u672c\u7684unicode\u51e0\u4e4e\u4e00\u6837\u3002
Notes
Python 2
Python 3
\u2460
u'PapayaWhip' 'PapayaWhip'
\u2461
ur'PapayaWhip\foo' r'PapayaWhip\foo'
Python 2\u91cc\u7684Unicode\u5b57\u7b26\u4e32\u5728Python 3\u91cc\u5373\u666e\u901a\u5b57\u7b26\u4e32\uff0c\u56e0\u4e3a\u5728Python 3\u91cc\u5b57\u7b26\u4e32\u603b\u662fUnicode\u5f62\u5f0f\u7684\u3002
Unicode\u539f\u59cb\u5b57\u7b26\u4e32(raw string)(\u4f7f\u7528\u8fd9\u79cd\u5b57\u7b26\u4e32\uff0cPython\u4e0d\u4f1a\u81ea\u52a8\u8f6c\u4e49\u53cd\u659c\u7ebf"\")\u4e5f\u88ab\u66ff\u6362\u4e3a\u666e\u901a\u7684\u5b57\u7b26\u4e32\uff0c\u56e0\u4e3a\u5728Python 3\u91cc\uff0c\u6240\u6709\u539f\u59cb\u5b57\u7b26\u4e32\u90fd\u662f\u4ee5Unicode\u7f16\u7801\u7684\u3002
\u5168\u5c40\u51fd\u6570unicode()
Python 2\u6709\u4e24\u4e2a\u5168\u5c40\u51fd\u6570\u53ef\u4ee5\u628a\u5bf9\u8c61\u5f3a\u5236\u8f6c\u6362\u6210\u5b57\u7b26\u4e32\uff1aunicode()\u628a\u5bf9\u8c61\u8f6c\u6362\u6210Unicode\u5b57\u7b26\u4e32\uff0c\u8fd8\u6709str()\u628a\u5bf9\u8c61\u8f6c\u6362\u4e3a\u975eUnicode\u5b57\u7b26\u4e32\u3002
Python 3\u53ea\u6709\u4e00\u79cd\u5b57\u7b26\u4e32\u7c7b\u578b\uff0cUnicode\u5b57\u7b26\u4e32\uff0c\u6240\u4ee5str()\u51fd\u6570\u5373\u53ef\u5b8c\u6210\u6240\u6709\u7684\u529f\u80fd\u3002(unicode()\u51fd\u6570\u5728Python 3\u91cc\u4e0d\u518d\u5b58\u5728\u4e86\u3002)
Notes
Python 2
Python 3
unicode(anything) str(anything)
5.\u6570\u636e\u7c7b\u578b
1\uff09Python 2\u6709\u4e3a\u975e\u6d6e\u70b9\u6570\u51c6\u5907\u7684int\u548clong\u7c7b\u578b\u3002int\u7c7b\u578b\u7684\u6700\u5927\u503c\u4e0d\u80fd\u8d85\u8fc7sys.maxint\uff0c\u800c\u4e14\u8fd9\u4e2a\u6700\u5927\u503c\u662f\u5e73\u53f0\u76f8\u5173\u7684\u3002\u53ef\u4ee5\u901a\u8fc7\u5728\u6570\u5b57\u7684\u672b\u5c3e\u9644\u4e0a\u4e00\u4e2aL\u6765\u5b9a\u4e49\u957f\u6574\u578b\uff0c\u663e\u7136\uff0c\u5b83\u6bd4int\u7c7b\u578b\u8868\u793a\u7684\u6570\u5b57\u8303\u56f4\u66f4\u5927\u3002
\u5728Python 3\u91cc\uff0c\u53ea\u6709\u4e00\u79cd\u6574\u6570\u7c7b\u578bint\uff0c\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u5b83\u5f88\u50cfPython 2\u91cc\u7684\u957f\u6574\u578b\u3002
Note:\u68c0\u67e5\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u662f\u6574\u578b\uff0c\u83b7\u5f97\u5b83\u7684\u6570\u636e\u7c7b\u578b\uff0c\u5e76\u4e0e\u4e00\u4e2aint\u7c7b\u578b(\u4e0d\u662flong)\u7684\u4f5c\u6bd4\u8f83\u3002\u4f60\u4e5f\u53ef\u4ee5\u4f7f\u7528isinstance()\u51fd\u6570\u6765\u68c0\u67e5\u6570\u636e\u7c7b\u578b\uff1b\u518d\u5f3a\u8c03\u4e00\u6b21\uff0c\u4f7f\u7528int\uff0c\u800c\u4e0d\u662flong\uff0c\u6765\u68c0\u67e5\u6574\u6570\u7c7b\u578b\u3002
sys.maxint
\u7531\u4e8e\u957f\u6574\u578b\u548c\u6574\u578b\u88ab\u6574\u5408\u5728\u4e00\u8d77\u4e86\uff0csys.maxint\u5e38\u91cf\u4e0d\u518d\u7cbe\u786e\u3002\u4f46\u662f\u56e0\u4e3a\u8fd9\u4e2a\u503c\u5bf9\u4e8e\u68c0\u6d4b\u7279\u5b9a\u5e73\u53f0\u7684\u80fd\u529b\u8fd8\u662f\u6709\u7528\u5904\u7684\uff0c\u6240\u4ee5\u5b83\u88abPython 3\u4fdd\u7559\uff0c\u5e76\u4e14\u91cd\u547d\u540d\u4e3asys.maxsize\u3002
Notes
Python 2
Python 3
\u2460
from sys import maxint from sys import maxsize
\u2461
python中python2和python3之间的转换方式如下:
一、放弃python 2.6之前的python版本
python 2.6之前的python版本缺少一些新特性，会给你的迁移工作带来不少麻烦。如果不是迫不得已还是放弃对之前版本的支持吧。
二、使用 2to3 工具对代码进行检查和转换
2to3是python自带的一个代码转换工具，可以将python2的代码自动转换为python3的代码。当然，不幸的是转换出的代码并没有对python2的兼容做任何的处理。所以我们并不真正使用2to3转换出的代码。执行2to3.py 查看输出信息，并修正相关问题。为了简化这个转换过程，这个脚本会将你的Python 2程序源文件作为输入，然后自动将其转换到Python 3的形式。
这简单！
访问网页链接这个网站就可以了！又自动转换的站点。
请注意！python2和python3是两种不同的语言，只是都属于python而已，所以不要自己直接改，相信电脑！
绛旓細绯荤粺鍖哄埆锛1銆丏ownload Windows X86 鍙緵鐢佃剳绯荤粺32浣嶄娇鐢ㄣ2銆丏ownload Windows X86-64 鍙緵鐢佃剳绯荤粺64浣嶄娇鐢ㄣ傜増鏈尯鍒細1銆丏ownload Windows X86 web-based installer 鏄氳繃闇瑕佽仈缃戝畬鎴愬畨瑁鐨鏂囦欢銆2銆丏ownload Windows X86 executable installer 鏄彲鎵ц鐨勫畨瑁呮枃浠讹紝涓嬭浇鍚庯紝鍙屽嚮瀹夎鍗冲彲銆3銆丏ownload ...
绛旓細1銆丳ython2涔嬪墠鏄潪甯稿彈娆㈣繋鐨勶紝鐜板湪寰堝杞欢鍏徃渚濈劧浣跨敤鐨勬槸Python2锛屼笉杩囩敱浜庤秺鏉ヨ秺澶氱殑鍏徃寮濮嬩粠Python2杩佺Щ鍒3锛屽洜姝ゅ垵瀛﹁呭彲浠ラ伩鍏嶈姳璐规洿澶氱殑鏃堕棿瀛︿範杩囧幓鐨勭増鏈簡銆2銆Python2鍜孭ython3涔嬮棿鏈変竴浜涙槸鏃犳硶浜掔浉鍏煎鐨勶紝鐜板湪寰堝寮鍙戜汉鍛橀兘鍦ㄤ娇鐢≒ython3寮鍙戝簱锛岃澶氳佺殑鍩轰簬Python2鐨勫紑鍙戝寘渚濈劧鏄棤娉曞吋瀹...
绛旓細閫夋嫨 閭ｆ槸瀛︿範 Python2 杩樻槸 Python 3鍛紵鐧芥湀榛戠窘璁や负锛氬鏋滀綘鏄竴涓垵瀛﹁咃紝鐧芥湀榛戠窘寤鸿浣犲彲浠 鐩存帴瀛︿範 Python 3锛屼粠杩欓噷寮濮嬪拰鐧芥湀榛戠窘涓璧峰涔燩ython3鍚!濡傛灉浣犳槸涓涓狿ython2 鐨勫紑鍙戣咃紝鐧芥湀榛戠窘涔熷缓璁厛浜嗚ВPython2鍜孭ython3鐨勫尯鍒紝浠ヤ究鎶婁綘鐨勪骇鍝佹棭鏃ュ崌绾ф敮鎸丳ython 3 Python3 鐩墠浣跨敤姣旇緝...
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