使用map和zip确定list中的顺序项是否等于1

Question

Python beginner here, looking for some guidance and insight. I have the following code that works in python:

z=0
y=0
valid=[]
test = [1,2,1,3,4,4,5,2,6,7]

for i, j in zip(test, test[1:]):
    if (j - i) == 1:
        z += 1
    valid.append(i)
    valid.append(j)
else:
    y += 1

print("There are " + str(len(test)) + " entries with " + str(z) + " sequential events and " + str(y) + " non-sequentual events")

print(list(valid))

This gives me the output I hope for:

There are 10 entries with 4 sequential events and 5 non-sequentual events
[1, 2, 3, 4, 4, 5, 6, 7]

I would prefer to be more Pythonic and I am trying to recreate this with map and zip:

map(diff_val(help_here_pls), zip(test, test[1:]))

I know that maps follows "map(function, iterable)". How can I get my map output to match my preferred list of

[1, 2, 3, 4, 4, 5, 6, 7]

using a function (the help_here_pls").

I know that:

• zip creates a tuple'd list
• map take a function and iterable (from my zip in this case)

Do I pass a tuple via the function in map? Can a lambda handle this, or do I need to define a separate function? Even if I can do that, do I have to unpack the tuple? (i ,j) = [passed tuple]

Thanks in advance for any guidance you can provide! reading / references welcomed!

Answer 1

A list comprehension is the pythonic choice here. I changed the result to give a list of tuples because the flattened list obscured that there is a relationship between each pair of items.

test = [1,2,1,3,4,4,5,2,6,7]
valid = [(i,j) for (i,j) in zip(test, test[1:]) if j-i == 1]
s = "There are {} entries with {} sequential events and {} non-sequentual events"
print(s.format(len(test), len(valid), len(test)-1-len(valid)))
print(valid)

Output:

There are 10 entries with 4 sequential events and 5 non-sequentual events
[(1, 2), (3, 4), (4, 5), (6, 7)]

Here's another way using more_itertools :

from operator import sub # function for subtraction
from more_itertools import flatten, pairwise

list(flatten(t for t in pairwise(test) if sub(*t)==-1))

gives

[1, 2, 3, 4, 4, 5, 6, 7]