utils.py 文件源码

def unique(lst):
    """
    Return unique elements

    :class:`pandas.unique` and :class:`numpy.unique` cast
    mixed type lists to the same type. They are faster, but
    some times we want to maintain the type.

    Parameters
    ----------
    lst : list-like
        List of items

    Returns
    -------
    out : list
        Unique items in the order that they appear in the
        input.

    Examples
    --------
    >>> import pandas as pd
    >>> import numpy as np
    >>> lst = ['one', 'two', 123, 'three']
    >>> pd.unique(lst)
    array(['one', 'two', '123', 'three'], dtype=object)
    >>> np.unique(lst)
    array(['123', 'one', 'three', 'two'],
          dtype='<U5')
    >>> unique(lst)
    ['one', 'two', 123, 'three']

    pandas and numpy cast 123 to a string!, and numpy does not
    even maintain the order.
    """
    seen = set()

    def make_seen(x):
        seen.add(x)
        return x

    return [make_seen(x) for x in lst if x not in seen]