How does `zip([iter(s)]*n)` efficiently split a list into equal chunks in Python?

Deconstructing zip([iter(s)]n) in Python

In Python, the zip() function combines elements from multiple iterables into a single iterable of tuples. When used with the syntax zip([iter(s)]n), it offers a convenient way to split a list into chunks of equal size.

How it Works:

The expression [iter(s)]n creates a list containing n copies of the iterator over the list s. Each copy of the iterator starts at the beginning of the list. The *args unpacks the list into arguments for zip(), resulting in n iterables being passed to the function.

Verbose Equivalent:

To recreate the functionality of zip([iter(s)]n) with verbose code:

def verbose_chunk(s, n):
  """Returns a list of chunks of equal size from a list."""
  chunks = []
  for i in range(n):
    chunk = []
    for j in range(len(s) // n):
      chunk.append(next(iter(s)))
    chunks.append(tuple(chunk))
  return chunks

This code first iterates over the desired number of chunks. For each chunk, it uses a nested loop to iterate over the elements in the list and add them to the chunk. The chunk is then converted into a tuple and added to the list of chunks.

Example:

s = [1,2,3,4,5,6,7,8,9]
n = 3

print(list(zip(*[iter(s)]*n)))  # [(1,2,3),(4,5,6),(7,8,9)]
print(verbose_chunk(s, n))  # [(1,2,3),(4,5,6),(7,8,9)]

Both approaches produce the same result, with the concise zip([iter(s)]n) expression offering a more efficient syntax for splitting lists into chunks.

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