python 2.7 - Error in exponential PDF -

i need complete function exponentialpdf error:

'indexerror: index 0 out of bounds axis 0 size 0'

the function looks this:

def uniformpdf(x,a=0.0,b=4.0):     p = 1.0/(b-a)*ones((len(x),))     p[x<a] = 0.0     p[x>b] = 0.0     return(p)  def exponentialpdf(x,a=1.0): """ call:    p = exponentialpdf(x,a) input argument:    vals: float (array) output argument:    p: float (array) examples:    in[1]:  exponentialpdf([1,2],3)    out[1]: array([ 0.14936121,  0.03332699]) """     p = * exp(-a*x)     p[x<0] = 0.0     return(p) 

can me error?

sounds list passing in function empty. read python lists , see following post: indexerror: list assignment index out of range

i found function works using numpy array, e.g. p = exponentialpdf(np.array([1,2]),3). hope help, should check out homework post , ask again if you're still stuck.

edit: using numpy, add explicit convert numpy array in function follows:

def exponentialpdf(x,a=1.0):     """     call:        p = exponentialpdf(x,a)     input argument:        vals: float (array)     output argument:         p: float (array)     examples:        in[1]:  exponentialpdf([1,2],3)        out[1]: array([ 0.14936121,  0.03332699])     """     if type(x) list:         x = array(x)      p = * exp(-a*x)     p[x<0] = 0.0     return(p) 

hopefully fix problem , can use function needed (assuming returning numpy array function okay).