[英]Sum one number to every element in a list (or array) in Python
Here I go with my basic questions again, but please bear with me. 在这里,我再次提出基本问题,但请耐心等待。
In Matlab, is fairly simple to add a number to elements in a list: 在Matlab中,将数字添加到列表中的元素非常简单:
a = [1,1,1,1,1]
b = a + 1
b
then is [2,2,2,2,2]
b
然后是[2,2,2,2,2]
In python this doesn't seem to work, at least on a list. 在python中,这似乎不起作用,至少在列表上。
Is there a simple fast way to add up a single number to the entire list. 有没有一种简单的快速方法可以将单个数字加到整个列表中。
Thanks 谢谢
if you want to operate with list of numbers it is better to use NumPy arrays: 如果要处理数字列表,最好使用NumPy数组:
import numpy
a = [1, 1, 1 ,1, 1]
ar = numpy.array(a)
print ar + 2
gives 给
[3, 3, 3, 3, 3]
using List Comprehension: 使用列表推导:
>>> L = [1]*5
>>> [x+1 for x in L]
[2, 2, 2, 2, 2]
>>>
which roughly translates to using a for loop: 大致翻译为使用for循环:
>>> newL = []
>>> for x in L:
... newL+=[x+1]
...
>>> newL
[2, 2, 2, 2, 2]
or using map: 或使用地图:
>>> map(lambda x:x+1, L)
[2, 2, 2, 2, 2]
>>>
You can also use map: 您还可以使用地图:
a = [1, 1, 1, 1, 1]
b = 1
list(map(lambda x: x + b, a))
It gives: 它给:
[2, 2, 2, 2, 2]
If you don't want list comprehensions: 如果您不希望列表理解:
a = [1,1,1,1,1]
b = []
for i in a:
b.append(i+1)
try this. 尝试这个。 (I modified the example on the purpose of making it non trivial) (我修改了这个示例,目的是使其变得不平凡)
import operator
import numpy as np
n=10
a = list(range(n))
a1 = [1]*len(a)
an = np.array(a)
operator.add
is almost more than two times faster operator.add
几乎快了两倍多
%timeit map(operator.add, a, a1)
than adding with numpy 比用numpy添加
%timeit an+1
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