list – Circular array indices in Python
list – Circular array indices in Python
You can use modulo operator, like this
print a[3 % len(a)]
If you dont want to use modulo operator like this, you need to subclass list
and implement __getitem__
, yourself.
class CustomList(list):
def __getitem__(self, index):
return super(CustomList, self).__getitem__(index % len(self))
a = CustomList([1, 2, 3])
for index in xrange(5):
print index, a[index]
Output
0 1
1 2
2 3
3 1
4 2
If you want to do the same with Numpy Arrays, you can do like this
import numpy as np
class CustomArray(np.ndarray):
def __new__(cls, *args, **kwargs):
return np.asarray(args[0]).view(cls)
def __getitem__(self, index):
return np.ndarray.__getitem__(self, index % len(self))
a = CustomArray([1, 2, 3])
for index in xrange(5):
print a[index]
More information about Subclassing Numpy Arrays can be found here (Thanks to JonClements)
Having such functionality is not good for your code. Instead write a generator function which generates you round robin values.
numbers = [1, 2, 3]
def returnNumber():
A circular array for yielding list members repeatedly
index = -1
while True:
index += 1
yield slangWords[index % len(numbers)]
# Now you can use this generator
numberGenerator = returnNumber()
numberGenerator.next() # returns 1
numberGenerator.next() # returns 2
numberGenerator.next() # returns 3
numberGenerator.next() # returns 1
numberGenerator.next() # returns 2
list – Circular array indices in Python
You can very simply:
mainArr = [5,2,1,4,2]
def getRangeArray(startIndexInMainArray):
s = mainArr[startIndexInMainArray::]
b=len(mainArr)-len(s)
return (s+mainArr[0:b])
print(mainArr)
print(getRangeArray(4)) # What is the first index?
#for index 4
#[5, 2, 1, 4, 2] before
#[2, 5, 2, 1, 4] after
#for index 2
#[5, 2, 1, 4, 2] before
#[1, 4, 2, 5, 2] after
#for index 0
#[5, 2, 1, 4, 2] before
#[5, 2, 1, 4, 2] after