'allocation_content_length' (#1808)

* 'allocation_content_length'

* 'allocation_number'

* Delete allocation_content_length.py

* Update allocation_number.py

* Update allocation_number.py

* number_of_bytes and partitions

* Update allocation_number.py

Co-authored-by: Christian Clauss <cclauss@me.com>

maths/allocation_number.py

@@ -0,0 +1,56 @@
+from typing import List
+
+
+def allocation_num(number_of_bytes: int, partitions: int) -> List[str]:
+    """
+    Divide a number of bytes into x partitions.
+    
+    In a multi-threaded download, this algorithm could be used to provide 
+    each worker thread with a block of non-overlapping bytes to download.
+    For example:
+        for i in allocation_list:
+            requests.get(url,headers={'Range':f'bytes={i}'})
+
+    parameter
+    ------------
+    : param number_of_bytes
+    : param partitions
+
+    return
+    ------------
+    : return: list of bytes to be assigned to each worker thread
+
+    Examples:
+    ------------
+    >>> allocation_num(16647, 4)
+    ['0-4161', '4162-8322', '8323-12483', '12484-16647']
+    >>> allocation_num(888, 888)
+    Traceback (most recent call last):
+        ...
+    ValueError: partitions can not >= number_of_bytes!
+    >>> allocation_num(888, 999)
+    Traceback (most recent call last):
+        ...
+    ValueError: partitions can not >= number_of_bytes!
+    >>> allocation_num(888, -4)
+    Traceback (most recent call last):
+        ...
+    ValueError: partitions must be a positive number!
+    """
+    if partitions <= 0:
+        raise ValueError('partitions must be a positive number!')
+    if partitions >= number_of_bytes:
+        raise ValueError('partitions can not >= number_of_bytes!')
+    bytes_per_partition = number_of_bytes // partitions
+    allocation_list = [f'0-{bytes_per_partition}']
+    for i in range(1, partitions - 1):
+        length = f'{bytes_per_partition * i + 1}-{bytes_per_partition * (i + 1)}'
+        allocation_list.append(length)
+    allocation_list.append(f'{(bytes_per_partition * (partitions - 1)) + 1}-'
+                           f'{number_of_bytes}')
+    return allocation_list
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()