Python extract elements from list with occasional pattern into a tuple

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I have a list that is has a pattern like this [float, string, float string...] but occasionally in the pattern it changes to [float, string, float, string, string, float string...]. What I want to do is to extract the elements of the list to a tuple in the format of (float, name, NoneType or str) to do something with it later. Here is a small example:

arr = [1150.1, 'James', 3323.1, 'Steve', 9323.1, 'John', 1233.1, 'Gary', 'criminal', 3293.1, 'Josh', 9232.1, 'Daniel', 'criminal']

I want to extract the list so the tuples look like this:

(1150.1, James, NONE)

(3323.1, Steve, NONE)

(9323.1, John, NONE)

(1233.1, Gary, criminal)

(3293.1, Josh, NONE)

(9232.1, Daniel, criminal)

so far i've tried checking for the next index in the array for the type but it's not working:

for index in range(len(arr)):
    if type(arr[index]) == float and type(arr[index+1]) == str:
        tup = arr[index], arr[index+1], None
        print(tup)
    elif type(arr[index]) == float and type(arr[index+1]) == str and type(arr[index+2]) == str:
        tup = arr[index], arr[index + 1], arr[index+2]
        print(tup)
extract tuples list python loops
3 Answers

You can keep track of the array elements you've seen since the last floating value using an auxiliary list. Whenever you see a float, turn the existing elements into a tuple and clear the auxiliary list:

result = []
items = []

for item in arr:
    if isinstance(item, float) and items:
        if len(items) < 3:
            items.append(None)
        result.append(tuple(items))
        items = [item]
    else:
        items.append(item)
    
result.append(tuple(items))

print(result)

This outputs:

[
 (1150.1, 'James', None), (3323.1, 'Steve', None),
 (9323.1, 'John', None), (1233.1, 'Gary', 'criminal'),
 (3293.1, 'Josh', None), (9232.1, 'Daniel', 'criminal')
]
user_177698150

You could check for the "float", "string" pattern and append accordingly:

output = list()
for i, element in enumerate(arr):
    if isinstance(element, float) and isinstance(arr[i+1], str):
        if isinstance(arr[i+2], str):
            t = tuple(arr[i:i+3])
        else:
            t = tuple(arr[i:i+2]+["NONE"])
        output.append(t)

>>> output
[(1150.1, 'James', 'NONE'),
 (3323.1, 'Steve', 'NONE'),
 (9323.1, 'John', 'NONE'),
 (1233.1, 'Gary', 'criminal'),
 (3293.1, 'Josh', 'NONE'),
 (9232.1, 'Daniel', 'criminal')]
user_98576310

Another solution:

from itertools import groupby

g1 = (g for v, g in groupby(arr, type) if v is float)
g2 = (g for v, g in groupby(arr, type) if v is str)

out = [(next(a), *[*b, None][:2]) for a, b in zip(g1, g2)]
print(out)

Prints:

[
    (1150.1, "James", None),
    (3323.1, "Steve", None),
    (9323.1, "John", None),
    (1233.1, "Gary", "criminal"),
    (3293.1, "Josh", None),
    (9232.1, "Daniel", "criminal"),
]
user_100359850
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