Issue #27720: Fix error in eng_to_decimal docs and add examples from the specification.
diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst
index 8d457e1..d164089 100644
--- a/Doc/library/decimal.rst
+++ b/Doc/library/decimal.rst
@@ -883,11 +883,13 @@
.. method:: to_eng_string([context])
- Convert to an engineering-type string.
+ Convert to a string, using engineering notation if an exponent is needed.
- Engineering notation has an exponent which is a multiple of 3, so there
- are up to 3 digits left of the decimal place. For example, converts
- ``Decimal('123E+1')`` to ``Decimal('1.23E+3')``.
+ Engineering notation has an exponent which is a multiple of 3. This
+ can leave up to 3 digits to the left of the decimal place and may
+ require the addition of either one or two trailing zeros.
+
+ For example, this converts ``Decimal('123E+1')`` to ``Decimal('1.23E+3')``.
.. method:: to_integral([rounding[, context]])
@@ -1453,7 +1455,11 @@
.. method:: to_eng_string(x)
- Converts a number to a string, using scientific notation.
+ Convert to a string, using engineering notation if an exponent is needed.
+
+ Engineering notation has an exponent which is a multiple of 3. This
+ can leave up to 3 digits to the left of the decimal place and may
+ require the addition of either one or two trailing zeros.
.. method:: to_integral_exact(x)
diff --git a/Lib/decimal.py b/Lib/decimal.py
index 4797a7d..e5329dd 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -1048,12 +1048,11 @@
return sign + intpart + fracpart + exp
def to_eng_string(self, context=None):
- """Convert to engineering-type string.
+ """Convert to a string, using engineering notation if an exponent is needed.
- Engineering notation has an exponent which is a multiple of 3, so there
- are up to 3 digits left of the decimal place.
-
- Same rules for when in exponential and when as a value as in __str__.
+ Engineering notation has an exponent which is a multiple of 3. This
+ can leave up to 3 digits to the left of the decimal place and may
+ require the addition of either one or two trailing zeros.
"""
return self.__str__(eng=True, context=context)
@@ -5339,9 +5338,29 @@
return r
def to_eng_string(self, a):
- """Converts a number to a string, using scientific notation.
+ """Convert to a string, using engineering notation if an exponent is needed.
+
+ Engineering notation has an exponent which is a multiple of 3. This
+ can leave up to 3 digits to the left of the decimal place and may
+ require the addition of either one or two trailing zeros.
The operation is not affected by the context.
+
+ >>> ExtendedContext.to_eng_string(Decimal('123E+1'))
+ '1.23E+3'
+ >>> ExtendedContext.to_eng_string(Decimal('123E+3'))
+ '123E+3'
+ >>> ExtendedContext.to_eng_string(Decimal('123E-10'))
+ '12.3E-9'
+ >>> ExtendedContext.to_eng_string(Decimal('-123E-12'))
+ '-123E-12'
+ >>> ExtendedContext.to_eng_string(Decimal('7E-7'))
+ '700E-9'
+ >>> ExtendedContext.to_eng_string(Decimal('7E+1'))
+ '70'
+ >>> ExtendedContext.to_eng_string(Decimal('0E+1'))
+ '0.00E+3'
+
"""
a = _convert_other(a, raiseit=True)
return a.to_eng_string(context=self)