Python data[i] to data[i+100] < # (eg. 50)

Question

I have a list containing a large amount of data. If I want to set a if statement as the pseudo code below:

if data[i] to data[i+100] < 50:
    data[i] == 1

Is there any way that I don't need to type something like below?

data[i] <50 and data[i+1] <50 and data[i+2] <50 and .... and data[i+100] <50: 

Because it'd just be too time consuming. If anyone knows the faster way, pls let me know. Appreciated!!

Answer 1

Yes, you can use all(..) for that over a slicing of the list:

if all(x < 50 for x in data[i:i+101]):
    data[i] = 1 # probably you want assignment?

You have to write i:i+101 as slicing (and not i:i+100 ), since the upper bound is exclusive .

Or you can use range(..) and save on making a slice-copy of the list:

if all(data[j] < 50 for j in range(i,i+101)):
    data[i] = 1 # probably you want assignment?

Note that although you do not type all these conditions separately, of course Python will still perform iteration (and evaluate at most 101 such expressions).

Answer 2

Sure. You can map over the values, checking your requirement, and then can use all to ensure that they meet it:

>>> data = range(1000)
>>> all(map(lambda i: i < 50, data[:100]))
# => True

To break down whats going on:

• data[:101] gets a slice of the first 101 items in the array
• map iterates over those items and returns a boolean if passed our check i < 50 . ie. the resulting list is [True, True, True, ...]
• all then checks that every value is True

Then you can replace the items with some smart slicing:

if all(map(lambda i: i < 50, data[:100])):
     data = [1] * 100 + data[100:]

Answer 3

是。

if all(data[i+k] < 50 for k in range(0,101)):