Why Does `zip()` in Python Return a List of 20 Tuples When Combining Three Lists?

Understanding Zip List Functionality in Python

In Python programming, the zip() function plays a crucial role in combining multiple lists into a single list of tuples. Each tuple represents a row, pairing corresponding elements from the input lists.

Consider the following code snippet:

x1, x2, x3 = stuff.calculations(withdataa)

zipall = zip(x1, x2, x3)

print("len of zipall %s" % len(zipall))

Unlike the expected result of three, the output is 20, indicating a fundamental misunderstanding.

Unveiling the Nature of Zipped Lists

When you zip together three lists with 20 elements each, the resulting list contains 20 tuples. Each tuple contains three elements, one from each of the input lists.

For instance:

In [1]: a = b = c = range(20)

In [2]: zip(a, b, c)
Out[2]:
[(0, 0, 0),
 (1, 1, 1),
 ...
 (17, 17, 17),
 (18, 18, 18),
 (19, 19, 19)]

Determining Tuple Length

To determine the length of each tuple, you can inspect the first element:

In [3]: result = zip(a, b, c)

In [4]: len(result[0])
Out[4]: 3

However, this approach may fail if the input lists are empty. Therefore, it's best to use a more robust method to determine the number of elements in each tuple.

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