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TypeError with map with no len()

john polo jpolo at mail.usf.edu
Mon Sep 25 12:44:19 EDT 2017 
Python List,

I am trying to make practice data for plotting purposes. I am using 
Python 3.6. The instructions I have are

import matplotlib.pyplot as plt
import math
import numpy as np
t = np.arange(0, 2.5, 0.1)
y1 = map(math.sin, math.pi*t)
plt.plot(t,y1)

However, at this point, I get a TypeError that says

object of type 'map' has no len()

In [6]: t
Out[6]:
array([ 0. ,  0.1,  0.2,  0.3,  0.4,  0.5,  0.6,  0.7, 0.8,  0.9,  1. ,
         1.1,  1.2,  1.3,  1.4,  1.5,  1.6,  1.7,  1.8, 1.9,  2. ,  2.1,
         2.2,  2.3,  2.4])
In [7]: y1
Out[7]: <map at 0x6927128>
In [8]: math.pi*t
Out[8]:
array([ 0.        ,  0.31415927,  0.62831853,  0.9424778 , 1.25663706,
         1.57079633,  1.88495559,  2.19911486,  2.51327412, 2.82743339,
         3.14159265,  3.45575192,  3.76991118,  4.08407045, 4.39822972,
         4.71238898,  5.02654825,  5.34070751,  5.65486678, 5.96902604,
         6.28318531,  6.59734457,  6.91150384,  7.2256631 , 7.53982237])

At the start of creating y1, it appears there is an array to iterate 
through for the math.sin function used in map(), but y1 doesn't appear 
to be saving any values. I expected y1 to hold a math.sin() output for 
each item in math.pi*t, but it appears to be empty. Am I 
misunderstanding map()? Is there something else I should be doing 
instead to populate y1?


John
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