Function create_mgr

pandas/tests/internals/test_internals.py:182–242

Construct BlockManager from string description. String description syntax looks similar to np.matrix initializer. It looks like this:: a,b,c: f8; d,e,f: i8 Rules are rather simple: * see list of supported datatypes in `create_block` method * components are semic

(descr, item_shape=None)

def create_mgr(descr, item_shape=None):
    """
    Construct BlockManager from string description.

    String description syntax looks similar to np.matrix initializer.  It looks
    like this::

        a,b,c: f8; d,e,f: i8

    Rules are rather simple:

    * see list of supported datatypes in `create_block` method
    * components are semicolon-separated
    * each component is `NAME,NAME,NAME: DTYPE_ID`
    * whitespace around colons & semicolons are removed
    * components with same DTYPE_ID are combined into single block
    * to force multiple blocks with same dtype, use '-SUFFIX'::

        "a:f8-1; b:f8-2; c:f8-foobar"

    """
    if item_shape is None:
        item_shape = (N,)

    offset = 0
    mgr_items = []
    block_placements = {}
    for d in descr.split(";"):
        d = d.strip()
        if not len(d):
            continue
        names, blockstr = d.partition(":")[::2]
        blockstr = blockstr.strip()
        names = names.strip().split(",")

        mgr_items.extend(names)
        placement = list(np.arange(len(names)) + offset)
        try:
            block_placements[blockstr].extend(placement)
        except KeyError:
            block_placements[blockstr] = placement
        offset += len(names)

    mgr_items = Index(mgr_items)

    blocks = []
    num_offset = 0
    for blockstr, placement in block_placements.items():
        typestr = blockstr.split("-")[0]
        blocks.append(
            create_block(
                typestr, placement, item_shape=item_shape, num_offset=num_offset
            )
        )
        num_offset += len(placement)

    sblocks = sorted(blocks, key=lambda b: b.mgr_locs[0])
    return BlockManager(