bsutils module

Contains various utilities programs:

• printargs: a decorator that reports the arguments of the function it decorates
• bs_name_func: returns the name of the current function or its callers
• bs_error_abort: reports on error and aborts execution
• final_s: whether a word should have a final 's'
• bs_switch: an improved switch statement
• find_first: returns the index of and the first item in an iterable that satisfies a condition
• print_stars: prints a title within lines of stars
• file_print_stars: does the same, to a file
• fstring_integer_with_significant_digits: rounds an integer and returns an f-string
• mkdir_if_needed: creates a directory if it does not exist
• bscomb: a combination \({n \choose k}\) operator
• bslog, bsxlogx, bsexp: \(C^2\) extensions of \(\log(x), x\log x, \exp(x)\), and their first two derivatives
• bs_projection_point: projects a point on a line in the plane.

Note

if the math looks strange in the documentation, just reload the page.

bs_error_abort(msg='error, aborting')

report error and abort

Parameters:

Name	Type	Description	Default
msg	str	a message	'error, aborting'

Returns:

Type	Description
None	prints the message and exits with code 1

Source code in bs_python_utils/bsutils.py

def bs_error_abort(msg: str = "error, aborting") -> None:
    """
    report error and abort

    Args:
        msg: a message

    Returns:
        prints the message and exits with code 1
    """
    print_stars(f"{bs_name_func(3)}: {msg}")
    sys.exit(1)

bs_name_func(back=2)

get the name of the current function, or further back in stack

Parameters:

Name	Type	Description	Default
back	int	2 is current function, 3 the function that called it etc	2

Returns:

Type	Description
str	the name of the function

Source code in bs_python_utils/bsutils.py

def bs_name_func(back: int = 2) -> str:
    """
    get the name of the current function, or further back in stack

    Args:
        back: 2 is current function, 3 the function that called it etc

    Returns:
        the name of the function
    """
    stack = traceback.extract_stack()
    *_, func_name, _ = stack[-back]
    return cast(str, func_name)

bs_projection_point(x, y, a, b, c)

projection of point (x,y) on line ax+by+c=0

Parameters:

Name	Type	Description	Default
x	float	y: coordinates	required
a	float	b: c: line parameters (as in ax+by+c=0)	required

Returns:

Name	Type	Description
x_proj	float	y_proj: coordinates of projection point
dist	float	distance of point from line

Source code in bs_python_utils/bsutils.py

def bs_projection_point(
    x: float, y: float, a: float, b: float, c: float
) -> tuple[float, float, float]:
    """
    projection of point (x,y) on line ax+by+c=0

    Args:
        x: y: coordinates
        a: b: c: line parameters (as in ax+by+c=0)

    Returns:
        x_proj: y_proj: coordinates of projection point
        dist: distance of point from line
    """
    a2b2 = a * a + b * b
    denom = sqrt(a2b2)
    value = a * x + b * y + c
    x_proj = x - a * value / a2b2
    y_proj = y - b * value / a2b2
    dist = abs(value) / denom
    return x_proj, y_proj, dist

bs_switch(match, dico, strict=True, default='no match')

a switch statement that allows for partial matches if strict is False

Parameters:

Name	Type	Description	Default
match	str	what we look for in the keys	required
dico	dict	a dictionary with string keys	required
strict	bool	if False, we accept a partial match	True
default	Any	what we return if no match is found	'no match'

Returns:

Type	Description
Any	the value for the match, or default

Examples:

>>> calc_dict = {
"plus": lambda x, y: x + y,
"minus": lambda x, y: x - y
}
>>> plus = bs_switch('plus', calc_dict, default="unintended function")
>>> minus = bs_switch('min', calc_dict, strict=False, default="unintended function")
>>> plus(6, 4)
10
>>> minus(6, 4)
2
>>> bs_switch('plu', calc_dict)
"no match"

Source code in bs_python_utils/bsutils.py

def bs_switch(
    match: str, dico: dict, strict: bool = True, default: Any = "no match"
) -> Any:
    """
    a switch statement that allows for partial matches if strict is False

    Args:
        match: what we look for in the keys
        dico: a dictionary with string keys
        strict: if `False`, we accept a partial match
        default: what we return if no match is found

    Returns:
        the value for the match, or `default`

    Examples:
        >>> calc_dict = {
        "plus": lambda x, y: x + y,
        "minus": lambda x, y: x - y
        }
        >>> plus = bs_switch('plus', calc_dict, default="unintended function")
        >>> minus = bs_switch('min', calc_dict, strict=False, default="unintended function")
        >>> plus(6, 4)
        10
        >>> minus(6, 4)
        2
        >>> bs_switch('plu', calc_dict)
        "no match"
    """
    if strict:
        return dico.get(match, default)
    else:
        try:
            key = next(k for k in dico if match in k)
            return dico[key]
        except StopIteration:
            return default

bscomb(n, k)

number of combinations of k among n {n \choose k}

Parameters:

Name	Type	Description	Default
n	int		required
k	int	should be smaller than n	required

Returns:

Type	Description
int	{n \choose k}.

Source code in bs_python_utils/bsutils.py

def bscomb(n: int, k: int) -> int:
    """
    number of combinations of k among n `{n \\choose k}`

    Args:
        n:
        k: should be smaller than n

    Returns:
        `{n \\choose k}`.
    """
    if not isinstance(n, int):
        bs_error_abort(f"n should be an integer, not {n}")
    if not isinstance(k, int):
        bs_error_abort(f"k should be an integer, not {k}")
    if n < k:
        bs_error_abort(f"k={k} should not be larger than n={n}")
    return factorial(n) // (factorial(k) * factorial(n - k))

bsexp(x, bigx=50.0, lowx=-50.0, deriv=0)

C^2-extends the exponential above bigx and below lowx perhaps with derivatives

Parameters:

Name	Type	Description	Default
x	float	argument	required
bigx	float	upper bound	50.0
lowx	float	lower bound	-50.0
deriv	int	if 1, also return first derivative; if 2, the first two derivatives	0

Returns:

Type	Description
float | TwoFloats | ThreeFloats	the exponential C^2-extended above bigx and below lowx
float | TwoFloats | ThreeFloats	perhaps with derivatives

Source code in bs_python_utils/bsutils.py

def bsexp(
    x: float,
    bigx: float = 50.0,
    lowx: float = -50.0,
    deriv: int = 0,
) -> float | TwoFloats | ThreeFloats:
    """
    `C^2`-extends the exponential above `bigx` and below `lowx`
    perhaps with derivatives

    Args:
        x: argument
        bigx: upper bound
        lowx: lower bound
        deriv: if 1, also return first derivative; if 2, the first two derivatives

    Returns:
        the exponential `C^2`-extended above `bigx` and below `lowx`
        perhaps with derivatives
    """
    if deriv not in [0, 1, 2]:
        bs_error_abort(f"deriv can only be 0, 1, or 2; not {deriv}")
    if lowx < x < bigx:
        expx = exp(x)
        if deriv == 0:
            return expx
        if deriv == 1:
            return expx, expx
        return expx, expx, expx
    elif x < lowx:
        return _bsexp_extend(x, deriv, lowx)
    else:
        return _bsexp_extend(x, deriv, bigx)

bslog(x, eps=1e-30, deriv=0)

extends the logarithm below eps by taking a second-order approximation perhaps with derivatives

Parameters:

Name	Type	Description	Default
x	float	argument	required
eps	float	lower bound	1e-30
deriv	int	if 1, also return first derivative; if 2, the first two derivatives	0

Returns:

Type	Description
float | TwoFloats | ThreeFloats	\ln(x) C^2-extended below eps, perhaps with derivatives

Source code in bs_python_utils/bsutils.py

def bslog(
    x: float, eps: float = 1e-30, deriv: int = 0
) -> float | TwoFloats | ThreeFloats:
    """
    extends the logarithm below `eps` by taking a second-order approximation
    perhaps with derivatives

    Args:
        x: argument
        eps: lower bound
        deriv: if 1, also return first derivative; if 2, the first two derivatives

    Returns:
        `\\ln(x)` `C^2`-extended below `eps`, perhaps with derivatives
    """
    if deriv not in [0, 1, 2]:
        bs_error_abort(f"deriv can only be 0, 1, or 2; not {deriv}")
    if x > eps:
        logx = log(x)
        if deriv == 0:
            return logx
        dlogx = 1.0 / x
        if deriv == 1:
            return logx, dlogx
        d2logx = -dlogx * dlogx
        return logx, dlogx, d2logx
    else:
        dx = 1.0 - x / eps
        log_smaller = log(eps) - dx - dx * dx / 2.0
        if deriv == 0:
            return log_smaller
        dlog_smaller = (1.0 + dx) / eps
        if deriv == 1:
            return log_smaller, dlog_smaller
        d2log_smaller = -1.0 / eps / eps
        return log_smaller, dlog_smaller, d2log_smaller

bsxlogx(x, eps=1e-30, deriv=0)

extends x \ln(x) below eps by making it go to zero in a C^2 extension perhaps with derivatives

Parameters:

Name	Type	Description	Default
x	float	argument	required
eps	float	lower bound	1e-30
deriv	int	if 1, also return first derivative; if 2, the first two derivatives	0

Returns:

Type	Description
float | TwoFloats | ThreeFloats	x \ln(x) C^2-extended below eps, perhaps with derivatives

Source code in bs_python_utils/bsutils.py

def bsxlogx(
    x: float, eps: float = 1e-30, deriv: int = 0
) -> float | TwoFloats | ThreeFloats:
    """
    extends `x \\ln(x)` below `eps` by making it go to zero in a `C^2` extension
    perhaps with derivatives

    Args:
        x: argument
        eps: lower bound
        deriv: if 1, also return first derivative; if 2, the first two derivatives

    Returns:
        `x \\ln(x)`  `C^2`-extended below `eps`, perhaps with derivatives
    """
    if deriv not in [0, 1, 2]:
        bs_error_abort(f"deriv can only be 0, 1, or 2; not {deriv}")
    if x > eps:
        logx = log(x)
        if deriv == 0:
            return x * logx
        if deriv == 1:
            return x * logx, 1.0 + logx
        return x * logx, 1.0 + logx, 1.0 / x
    else:
        logeps = log(eps)
        dx = x / eps
        log_smaller = x * logeps - eps / 2.0 + x * dx / 2.0
        if deriv == 0:
            return log_smaller
        if deriv == 1:
            return log_smaller, logeps + dx
        return log_smaller, logeps + dx, 1.0 / eps

file_print_stars(file_handle, title=None, n=70)

Write the print_stars output to a file-like object.

Source code in bs_python_utils/bsutils.py

def file_print_stars(
    file_handle: TextIOBase, title: str | None = None, n: int = 70
) -> None:
    """Write the ``print_stars`` output to a file-like object."""
    line_stars = "*" * n
    file_handle.write("\n")
    file_handle.write(line_stars)
    file_handle.write("\n")
    if title:
        file_handle.write(title.center(n))
        file_handle.write("\n")
        file_handle.write(line_stars)
        file_handle.write("\n")
    file_handle.write("\n")

final_s(n, word)

pluralizes word if n > 1

Parameters:

Name	Type	Description	Default
n	int	how many times	required
word	str	to be pluralized, maybe	required

Returns:

Type	Description
str	1 word or n words

Source code in bs_python_utils/bsutils.py

def final_s(n: int, word: str) -> str:
    """
    pluralizes word if n > 1

    Args:
        n: how many times
        word: to be pluralized, maybe

    Returns:
        `1 word` or `n words`
    """
    return f"{n} {word}{'s' if n > 1 else ''}"

find_first(iterable, condition=lambda x: True)

Returns the index of and the first item in the iterable that satisfies the condition.

Parameters:

Name	Type	Description	Default
iterable	Iterable	where to look	required
condition	Callable	must return a boolean	lambda x: True

Returns:

Type	Description
Any	If the condition is not given, returns 0 and the first item of
Any	the iterable.
Any	Raises StopIteration if no item satisfyng the condition is found.

Examples:

>>> find_first( (1,2,3), condition=lambda x: x % 2 == 0)
(1, 2)
>>> find_first(range(3, 100))
(0, 3)
>>> find_first( () )
Traceback (most recent call last):
...
StopIteration

Source code in bs_python_utils/bsutils.py

def find_first(iterable: Iterable, condition: Callable = lambda x: True) -> Any:
    """
    Returns the index of and the first item in the `iterable` that
    satisfies the `condition`.

    Args:
        iterable: where to look
        condition: must return a boolean

    Returns:
        If the condition is not given, returns 0 and the first item of
        the iterable.

        Raises `StopIteration` if no item satisfyng the condition is found.

    Examples:
        >>> find_first( (1,2,3), condition=lambda x: x % 2 == 0)
        (1, 2)
        >>> find_first(range(3, 100))
        (0, 3)
        >>> find_first( () )
        Traceback (most recent call last):
        ...
        StopIteration


    """
    return next((i, x) for i, x in enumerate(iterable) if condition(x))

fstring_integer_with_significant_digits(number, m)

returns an f-string with number rounded to m significant digits

Parameters:

Name	Type	Description	Default
number	int	the integer we want to round	required
m	int	how many digits we keep; the rest is filled with zeroes	required

Return

a string with the rounded integer

Examples:

fstring_integer_with_significant_digits(12345, 0) ' 0' fstring_integer_with_significant_digits(12345, 3) '12,300' fstring_integer_with_significant_digits(12345, 7) '12345'

Source code in bs_python_utils/bsutils.py

def fstring_integer_with_significant_digits(number: int, m: int) -> str:
    """returns an f-string with `number` rounded to `m` significant digits

    Args:
        number: the integer we want to round
        m:  how many digits we keep; the rest is filled with zeroes

    Return:
        a string with the rounded integer

    Examples:
    >>> fstring_integer_with_significant_digits(12345, 0)
    ' 0'
    >>> fstring_integer_with_significant_digits(12345, 3)
    '12,300'
    >>> fstring_integer_with_significant_digits(12345, 7)
    '12345'
    """
    if (not isinstance(number, int)) or (not isinstance(m, int)):
        bs_error_abort("Both arguments should be integers.")
    if number == 0:
        return f"{number:d}"
    else:
        digits = len(str(abs(int(number))))
        if digits <= m:
            return f"{int(number):d}"
        else:
            power = digits - m
            rounded = round(number / 10**power) * 10**power
            return f"{int(rounded): ,d}"

mkdir_if_needed(p)

create the directory if it does not exist

Parameters:

Name	Type	Description	Default
p	Path | str	a path	required

Returns:

Type	Description
Path	the directory Path

Source code in bs_python_utils/bsutils.py

def mkdir_if_needed(p: Path | str) -> Path:
    """
    create the directory if it does not exist

    Args:
        p: a path

    Returns:
        the directory Path

    """
    try:
        q = Path(p)
    except OSError:
        bs_error_abort(f"{p} is not a path")
    if not q.exists():
        q.mkdir(parents=True)
    return q

print_stars(title=None, n=70)

Print a horizontal bar of * characters, optionally framing a title.

Parameters:

Name	Type	Description	Default
title	str | None	Optional text centred between two star lines.	None
n	int	Length of the star line.	70

Source code in bs_python_utils/bsutils.py

def print_stars(title: str | None = None, n: int = 70) -> None:
    """Print a horizontal bar of ``*`` characters, optionally framing a title.

    Args:
        title: Optional text centred between two star lines.
        n: Length of the star line.
    """
    line_stars = "*" * n
    print()
    print(line_stars)
    if title:
        print(title.center(n))
        print(line_stars)
    print()

printargs(func)

Decorator that reports the arguments of the function

Parameters:

Name	Type	Description	Default
func	Callable	the decorated function	required

Source code in bs_python_utils/bsutils.py

def printargs(func: Callable) -> Callable:
    """
    Decorator that reports the arguments of the function

    Args:
      func: the decorated function
    """

    @wraps(func)
    def wrapper(*args, **kwargs):
        print(
            f"Function {func.__name__} called with args = {args} and kwargs = {kwargs}"
        )
        return func(*args, **kwargs)

    return wrapper