Source code for datascience.formats

"""String formatting for table entries."""

__all__ = ['default_formatter', 'Formatter', 'NumberFormatter',
           'CurrencyFormatter', 'DateFormatter', 'PercentFormatter',
           'DistributionFormatter']


import numpy as np

from datetime import datetime, timezone


[docs]class Formatter: """String formatter that truncates long values.""" min_width = 4 max_width = 60 etc = ' ...' def __init__(self, min_width=None, max_width=None, etc=None): if min_width is not None: self.min_width = min_width if max_width is not None: self.max_width = max_width if etc is not None: self.etc = etc
[docs] def format_column(self, label, column): """Return a formatting function that pads & truncates values.""" if len(column) == 0: val_width = 0 else: val_width = max(len(self.format_value(v)) for v in column) val_width = min(val_width, self.max_width) width = max(val_width, len(str(label)), self.min_width, len(self.etc)) def pad(value, label=False): if label: raw = value else: raw = self.format_value(value) if len(raw) > width: prefix = raw[:width-len(self.etc)] + self.etc else: prefix = raw return prefix.ljust(width) return pad
[docs] @staticmethod def format_value(value): """Pretty-print an arbitrary value.""" if isinstance(value, (bool, np.bool_)): return str(value) elif isinstance(value, (int, np.integer)): return '{:n}'.format(value) elif isinstance(value, (float, np.floating)): return '{:g}'.format(value) else: return str(value)
[docs] def convert_column(self, values): """Convert each value using the the convert_value method.""" return list(map(self.convert_value, values))
[docs] @staticmethod def convert_value(value): """Identity conversion (override to convert values).""" return value
@property def converts_values(self): """Whether this Formatter also converts values.""" return self.convert_value is not Formatter.convert_value or \ self.convert_column is not Formatter.convert_column
default_formatter = Formatter() class FunctionFormatter(Formatter): """Format values using a function.""" def __init__(self, fn): self.format_value = lambda v: str(fn(v))
[docs]class NumberFormatter(Formatter): """Format numbers that may have delimiters.""" def __init__(self, decimals=2, decimal_point='.', separator=',', *args, **vargs): super().__init__(*args, **vargs) self.decimals = decimals self.decimal_point = decimal_point self.separator = separator
[docs] def convert_value(self, value): """Convert string 93,000.00 to float 93000.0.""" if isinstance(value, str): value = value.replace(self.separator, '') if self.decimal_point not in value: return int(value) else: return float(value.replace(self.decimal_point, '.')) else: return value
[docs] def format_value(self, value): if isinstance(value, (int, np.integer)): return ('{:' + self.separator + 'd}').format(value) else: return ('{:' + self.separator + '.' + str(self.decimals) + 'f}').format(value)
[docs]class CurrencyFormatter(Formatter): """Format currency and convert to float.""" def __init__(self, symbol="$", *args, **vargs): super().__init__(*args, **vargs) assert isinstance(symbol, str) self.symbol = symbol
[docs] def convert_value(self, value): """Convert value to float. If value is a string, ensure that the first character is the same as symbol ie. the value is in the currency this formatter is representing. """ if isinstance(value, str): assert value.startswith(self.symbol), "Currency does not start with " + self.symbol return float(value.lstrip(self.symbol)) return float(value)
[docs] def format_value(self, value): """Format currency.""" return self.symbol + "{0:,.2f}".format(value)
[docs]class DateFormatter(Formatter): """Format date & time and convert to UNIX timestamp.""" def __init__(self, format="%Y-%m-%d %H:%M:%S.%f", *args, **vargs): super().__init__(*args, **vargs) assert isinstance(format, str) self.format = format
[docs] def convert_value(self, value): """Convert 2015-08-03 to a Unix timestamp int.""" return datetime.strptime(value, self.format).timestamp()
[docs] def format_value(self, value): """Format timestamp as a string.""" return datetime.fromtimestamp(value).strftime(self.format)
[docs]class PercentFormatter(Formatter): """Format a number as a percentage.""" def __init__(self, decimals=2, *args, **vargs): super().__init__(*args, **vargs) assert isinstance(decimals, int) self.decimals = decimals
[docs] def format_value(self, value): """Format number as percentage.""" return ('{:.' + str(self.decimals) + '%}').format(value)
[docs]class DistributionFormatter(PercentFormatter): """Normalize a column and format as percentages."""
[docs] def convert_column(self, values): """Normalize values.""" assert all(values >= 0), 'Cannot normalize a column with negatives' total = sum(values) if total > 0: return values / total else: return values