I want to take step value in a for loop from an array. some thing like,
step = [0,1,2,15,3,87] #values in no order
for i in range(0, len(raw_pkt), step):
The step value should be updated in each iteration. Is there any workaround for that? I know that range() expects an integer value not a list. But I want to take values from the list on each iteration.
step:If you think about what you are trying to achieve, you don't really care about the list that you are trying to index as the step values are fixed. So even if the length of the raw_pkt was a million, because your step list is only length 6, you will only ever have 6 indexes.
Once you realise this, the code becomes pretty simple, you just want to iterate over the step values and increment a variable. This variable can be used to index a list or whatever, but this doesn't matter.
This makes the code pretty short and concise:
step = [0, 1, 2, 15, 3, 87]
i = 0
for s in step:
i += s
#code...
so to demonstrate that this works, we can do a more easy-to-follow example:
step = [0, 1, 2, 4, 1]
l = [5, 6, 3, 6, 2, 7, 3, 1, 8]
i = 0
for s in step:
i += s
print(i, l[i])
which outputs:
0 5
1 6
3 6
7 1
8 8
Hope this helps!
I guess what you want ist itertools.accumulate.
from itertools import accumulate
for i in accumulate([0,1,2,15,3,87]):
print(i)
# would print 0 1 3 18 21 108
there's an easy solution to this:
for pkt in [raw_pkt[i] for i in step]:
print pkt
with
step = [0,1,2,15,3,87]
and
raw_pkt = [100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199]
the result would be
100
101
102
115
103
187
indexes, not the values from the raw_pkt list...list-comprehension: [raw_pkt[i] for i in step] to a generator which is more efficient. i.e (raw_pkt[i] for i in step).step - unless step contains values for which you want the index in raw_pkt in which case simply change the foor loop from for pkt in [raw_pkt[i] for i in step] to for pkt_idx in [raw_pkt.index(i) for i in step]step values between the indexes, so a normal range such as for i in range(10) would have a step list of [1, 1, 1, ...]step = [0,1,2,15,3,87] #values in no order for i in range(0, len(raw_pkt), step):
laststp = 0
for stp in step:
for i in range(stp-laststp, len(raw_pkt), stp):
#do something
laststp = stp
break #this should make sure that each step is applied once.
whileloop. Arange(..)is constructed once.