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I'm running the following python script:
#!/usr/bin/python import os,sys from scipy import stats import numpy as np f=open('data2.txt', 'r').readlines() N=len(f)-1 for i in range(0,N): w=f[i].split() l1=w[1:8] l2=w[8:15] list1=[float(x) for x in l1] list2=[float(x) for x in l2] result=stats.ttest_ind(list1,list2) print result[1] However I got the errors like:
ValueError: could not convert string to float: id I'm confused by this. When I try this for only one line in interactive section, instead of for loop using script:
>>> from scipy import stats >>> import numpy as np >>> f=open('data2.txt','r').readlines() >>> w=f[1].split() >>> l1=w[1:8] >>> l2=w[8:15] >>> list1=[float(x) for x in l1] >>> list1 [5.3209183842, 4.6422726719, 4.3788135547, 5.9299061614, 5.9331108706, 5.0287087832, 4.57...] It works well.
Can anyone explain a little bit about this? Thank you.
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The Python "ValueError: could not convert string to float" occurs when we pass a string that cannot be converted to a float (e.g. an empty string or one containing characters) to the float() class. To solve the error, remove all unnecessary characters from the string.
The error ValueError: could not convert string to float occurs if you try to convert a string to a float that contains invalid characters. To solve this error, check the string for characters that you can remove and use the strip() method to get rid of them.
We can convert a string to float in Python using the float() function. This is a built-in function used to convert an object to a floating point number. Internally, the float() function calls specified object __float__() function.
Float() is a method that returns a floating-point number for a provided number or string. Float() returns the value based on the argument or parameter value that is being passed to it. If no value or blank parameter is passed, it will return the values 0.0 as the floating-point output.
Obviously some of your lines don't have valid float data, specifically some line have text id which can't be converted to float.
When you try it in interactive prompt you are trying only first line, so best way is to print the line where you are getting this error and you will know the wrong line e.g.
#!/usr/bin/python import os,sys from scipy import stats import numpy as np f=open('data2.txt', 'r').readlines() N=len(f)-1 for i in range(0,N): w=f[i].split() l1=w[1:8] l2=w[8:15] try: list1=[float(x) for x in l1] list2=[float(x) for x in l2] except ValueError,e: print "error",e,"on line",i result=stats.ttest_ind(list1,list2) print result[1] My error was very simple: the text file containing the data had some space (so not visible) character on the last line.
As an output of grep, I had 45 instead of just 45.
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