【问题】
有这样的字符串，是以e为底的，自然对数值：
| 2.1690427e-005 -1.1694737e-003 -6.1193734e-004 8.9455025e-004 -8.6277081e-004 -7.2735757e-004 |
想要将每个值，都转换为对应的浮点数值。
【解决过程】
1.参考：
和
去先试试：
1 2 | import math;print "math.e=",math.e; |
可以打印出对应的值：
| math.e= 2.71828182846 |
2.知道有个math.exp了，
就去Python手册中找找对应语法。
找到的是：
math.exp(x) Return e**x.
但是还是没有找到，如何转换成整数的。
3.但是看到了：
math.pow(x, y) Return x raised to the power y. Exceptional cases follow Annex ‘F’ of the C99 standard as far as possible. In particular, pow(1.0, x) and pow(x, 0.0) always return 1.0, even when x is a zero or a NaN. If both x and y are finite, x is negative, and y is not an integer then pow(x, y) is undefined, and raises ValueError.
Changed in version 2.6: The outcome of 1**nan and nan**0 was undefined.
所以，想要了，先去解析上述数据，得到对应的e的power的值，和对应的前缀的值，就可以获得对应数据了。
所以去尝试写代码，好像就可以了：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | #!/usr/bin/python# -*- coding: utf-8 -*-"""Function:关于python的sys 模块问题Author: Crifan LiVersion: 2012-12-13Contact: admin at crifan dot com"""import re;import math;def parseIntEValue(): print "math.e=",math.e; #math.e= 2.71828182846 intEValuesStr = """2.1690427e-005 -1.1694737e-003 -6.1193734e-004 8.9455025e-004 -8.6277081e-004 -7.2735757e-004"""; print "intEValuesStr=",intEValuesStr; intEStrList = re.findall("-?\d+\.\d+e-\d+", intEValuesStr); print "intEStrList=",intEStrList; for eachIntEStr in intEStrList: # intValue = int(eachIntEStr); # print "intValue=",intValue; foundEPower = re.search("(?P<intPart>-?\d+\.\d+)e(?P<ePower>-\d+)", eachIntEStr); #print "foundEPower=",foundEPower; if(foundEPower): intPart = foundEPower.group("intPart"); ePower = foundEPower.group("ePower"); #print "intPart=%s,ePower=%s"%(intPart, ePower); intPartValue = float(intPart); ePowerValue = float(ePower); print "intPartValue=%f,ePowerValue=%f"%(intPartValue, ePowerValue); wholeOrigValue = intPartValue * math.pow(math.e, ePowerValue); print "wholeOrigValue=",wholeOrigValue;if __name__ == "__main__": parseIntEValue(); |
然后再封装成函数，就变成了：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 | #!/usr/bin/python# -*- coding: utf-8 -*-"""Function:关于python的sys 模块问题Author: Crifan LiVersion: 2012-12-13Contact: admin at crifan dot com"""import re;import math;def ConvertELogStrToValue(eLogStr): """ convert string of natural logarithm base of E to value return (convertOK, convertedValue) eg: input: -1.1694737e-003 output: -0.0582246670563 input: 8.9455025e-004 output: 0.163843 """ (convertOK, convertedValue) = (False, 0.0); foundEPower = re.search("(?P<coefficientPart>-?\d+\.\d+)e(?P<ePowerPart>-\d+)", eLogStr, re.I); #print "foundEPower=",foundEPower; if(foundEPower): coefficientPart = foundEPower.group("coefficientPart"); ePowerPart = foundEPower.group("ePowerPart"); #print "coefficientPart=%s,ePower=%s"%(coefficientPart, ePower); coefficientValue = float(coefficientPart); ePowerValue = float(ePowerPart); #print "coefficientValue=%f,ePowerValue=%f"%(coefficientValue, ePowerValue); #math.e= 2.71828182846 wholeOrigValue = coefficientValue * math.pow(math.e, ePowerValue); #print "wholeOrigValue=",wholeOrigValue; (convertOK, convertedValue) = (True, wholeOrigValue); else: (convertOK, convertedValue) = (False, 0.0); return (convertOK, convertedValue);def parseIntEValue(): intEValuesStr = """2.1690427e-005 -1.1694737e-003 -6.1193734e-004 8.9455025e-004 -8.6277081e-004 -7.2735757e-004"""; print "intEValuesStr=",intEValuesStr; intEStrList = re.findall("-?\d+\.\d+e-\d+", intEValuesStr); print "intEStrList=",intEStrList; for eachIntEStr in intEStrList: # intValue = int(eachIntEStr); # print "intValue=",intValue; (convertOK, convertedValue) = ConvertELogStrToValue(eachIntEStr); #print "convertOK=%s,convertedValue=%f"%(convertOK, convertedValue); print "eachIntEStr=%s,\tconvertedValue=%f"%(eachIntEStr, convertedValue);# intEValuesStr= 2.1690427e-005 -1.1694737e-003 -6.1193734e-004# 8.9455025e-004 -8.6277081e-004 -7.2735757e-004# intEStrList= ['2.1690427e-005', '-1.1694737e-003', '-6.1193734e-004', '8.9455025e-004', '-8.6277081e-004', '-7.2735757e-004']# eachIntEStr=2.1690427e-005, convertedValue=0.014615# eachIntEStr=-1.1694737e-003, convertedValue=-0.058225# eachIntEStr=-6.1193734e-004, convertedValue=-0.112080# eachIntEStr=8.9455025e-004, convertedValue=0.163843# eachIntEStr=-8.6277081e-004, convertedValue=-0.158022# eachIntEStr=-7.2735757e-004, convertedValue=-0.133220if __name__ == "__main__": parseIntEValue(); |
【总结】
Python中，没有直接可以把以e为底的自然对数的字符串，强制转换成对应的数值的。
需要自己实现对应的代码才行。