Do you hate Python’s range() and want to use R’s seq()?

I do. So I implemented R’s function in Python.

I wrote a bunch of tests for this for most uses I could think of and they all work. Except the length param, which I did not implement so far. Did not need it. It can be implemented by simply generating the desired number of natural numbers beginning from 1, and then rescaling this to the desired range.

 

#R style seq()
def seq(from_ = None, to = None, by = None, length = None, along = None):
    #init
    falling = False

    #length
    if not length is None:
        #TODO: implement when needed
        raise ValueError("`length` is not implemented yet")

    #along object
    if not along is None:
        return list(range(1, len(along) + 1))

    #if all numeric None, set defaults
    if from_ is None and to is None and by is None:
        to = 1
        from_ = 1

    #1 argument
    if not from_ is None and to is None and by is None:
        #this is actually to
        to = from_
        from_ = 1

    #determine by and adjustment
    if from_ > to:
        adjustment = -1

        #set by
        if by is None:
            by = -1
    else:
        adjustment = 1

        #set by
        if by is None:
            by = 1

    #impossible by
    if from_ > to and by > 0:
        raise ValueError("`by` cannot be positive when falling direction")
    if from_ < to and by < 0:
        raise ValueError("`by` cannot be negative when increasing direction")
    if by is 0:
        raise ValueError("`by` cannot be zero")

    #from, to
    if not from_ is None and not to is None:

        return list(range(from_, to + adjustment, by))


    #if you get here, something is wrong!
    raise ValueError("Unknown error. Bad input?")


#convenience wrapper
def seq_along(x):
    return(seq(along = x))

 

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