如何将两个列表中的元素组合成第三个？

Question

I have two lists a and b :

a  =   [3,    6,   8,   65,   3]
b  =   [34,   2,   5,   3,    5]

c gets [3/34, 6/2, 8/5, 65/3, 3/5]

Is it possible to obtain their ratio in Python, like in variable c above?

I tried a/b and got the error:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for /: 'list' and 'list'

Answer 1

>>> from __future__ import division # floating point division in Py2x
>>> a=[3,6,8,65,3]
>>> b=[34,2,5,3,5]
>>> [x/y for x, y in zip(a, b)]
[0.08823529411764706, 3.0, 1.6, 21.666666666666668, 0.6]

Or in numpy you can do a/b

>>> import numpy as np
>>> a=np.array([3,6,8,65,3], dtype=np.float)
>>> b=np.array([34,2,5,3,5], dtype=np.float)
>>> a/b
array([  0.08823529,   3.        ,   1.6       ,  21.66666667,   0.6       ])

Answer 2

The built-in map() function makes short work of these kinds of problems:

>>> from operator import truediv
>>> a=[3,6,8,65,3]
>>> b=[34,2,5,3,5]
>>> map(truediv, a, b)
[0.08823529411764706, 3.0, 1.6, 21.666666666666668, 0.6]

Answer 3

You can do this using list comprehension (element by element):

div = [ai/bi for ai,bi in zip(a,b)]

Note that if you want float division, you need to specify this (or make the original values floats):

fdiv = [float(ai)/bi for ai,bi in zip(a,b)]

Answer 4

Use zip and a list comprehension:

>>> a = [3,6,8,65,3]
>>> b = [34,2,5,3,5]
>>> [(x*1.0)/y for x, y in zip(a, b)]
[0.08823529411764706, 3.0, 1.6, 21.666666666666668, 0.6]

Answer 5

使用numpy.divide

c=np.divide(a,b)

Answer 6

You can use the following code:

a  =   [3,    6,   8,   65,   3]
b  =   [34,   2,   5,   3,    5]

c = [float(x)/y for x,y in zip(a,b)]
print(c)