With numeric values in a gt table, we can perform currency-based formatting with the fmt_currency() method. This supports both automatic formatting with a three-letter currency code. We have fine control over the conversion from numeric values to currency values, where we could take advantage of the following options:
the currency: providing a currency code or common currency name will procure the correct currency symbol and number of currency subunits
currency symbol placement: the currency symbol can be placed before or after the values
decimals/subunits: choice of the number of decimal places, and a choice of the decimal symbol, and an option on whether to include or exclude the currency subunits (the decimal portion)
digit grouping separators: options to enable/disable digit separators and provide a choice of separator symbol
scaling: we can choose to scale targeted values by a multiplier value
pattern: option to use a text pattern for decoration of the formatted currency values
locale-based formatting: providing a locale ID will result in currency formatting specific to the chosen locale; it will also retrieve the locale’s currency if none is explicitly given
Parameters
columns:SelectExpr=None
The columns to target. Can either be a single column name or a series of column names provided in a list.
rows:int | list[int] | None=None
In conjunction with columns=, we can specify which of their rows should undergo formatting. The default is all rows, resulting in all rows in targeted columns being formatted. Alternatively, we can supply a list of row indices.
currency:str | None=None
The currency to use for the numeric value. This input can be supplied as a 3-letter currency code (e.g., "USD" for U.S. Dollars, "EUR" for the Euro currency).
use_subunits:bool=True
An option for whether the subunits portion of a currency value should be displayed. For example, with an input value of 273.81, the default formatting will produce "$273.81". Removing the subunits (with use_subunits = False) will give us "$273".
decimals:int | None=None
The decimals values corresponds to the exact number of decimal places to use. This value is optional as a currency has an intrinsic number of decimal places (i.e., the subunits). A value such as 2.34 can, for example, be formatted with 0 decimal places and if the currency used is "USD" it would result in "$2". With 4 decimal places, the formatted value becomes "$2.3400".
drop_trailing_dec_mark:bool=True
A boolean value that determines whether decimal marks should always appear even if there are no decimal digits to display after formatting (e.g., 23 becomes 23. if False). By default trailing decimal marks are not shown.
use_seps:bool=True
The use_seps option allows for the use of digit group separators. The type of digit group separator is set by sep_mark and overridden if a locale ID is provided to locale. This setting is True by default.
scale_by:float=1
All numeric values will be multiplied by the scale_by value before undergoing formatting. Since the default value is 1, no values will be changed unless a different multiplier value is supplied.
pattern:str='{x}'
A formatting pattern that allows for decoration of the formatted value. The formatted value is represented by the {x} (which can be used multiple times, if needed) and all other characters will be interpreted as string literals.
sep_mark:str=','
The string to use as a separator between groups of digits. For example, using sep_mark="," with a value of 1000 would result in a formatted value of "1,000". This argument is ignored if a locale is supplied (i.e., is not None).
dec_mark:str='.'
The string to be used as the decimal mark. For example, using dec_mark="," with the value 0.152 would result in a formatted value of "0,152"). This argument is ignored if a locale is supplied (i.e., is not None).
force_sign:bool=False
Should the positive sign be shown for positive values (effectively showing a sign for all values except zero)? If so, use True for this option. The default is False, where only negative numbers will display a minus sign.
placement:str='left'
The placement of the currency symbol. This can be either be "left" (as in "$450") or "right" (which yields "450$").
incl_space:bool=False
An option for whether to include a space between the value and the currency symbol. The default is to not introduce a space character.
locale:str | None=None
An optional locale identifier that can be used for formatting values according the locale’s rules. Examples include "en" for English (United States) and "fr" for French (France).
The GT object is returned. This is the same object that the method is called on so that we can facilitate method chaining.
Adapting output to a specific locale
This formatting method can adapt outputs according to a provided locale value. Examples include "en" for English (United States) and "fr" for French (France). The use of a valid locale ID here means separator and decimal marks will be correct for the given locale. Should any values be provided in sep_mark or dec_mark, they will be overridden by the locale’s preferred values. In addition to number formatting, providing a locale value and not providing a currency allows Great Tables to obtain the currency code from the locale’s territory.
Note that a locale value provided here will override any global locale setting performed in GT()’s own locale argument (it is settable there as a value received by all other methods that have a locale argument).
Examples
Let’s use the exibble dataset to create a table. With the fmt_currency() method, we’ll format the currency column to display monetary values.