Display a decimal in scientific notation
PythonString FormattingNumber FormattingScientific NotationPython Problem Overview
How can I display this:
Decimal('40800000000.00000000000000') as '4.08E+10'?
I've tried this:
>>> '%E' % Decimal('40800000000.00000000000000')
'4.080000E+10'
But it has those extra 0's.
Python Solutions
Solution 1 - Python
from decimal import Decimal
'%.2E' % Decimal('40800000000.00000000000000')
# returns '4.08E+10'
In your '40800000000.00000000000000' there are many more significant zeros that have the same meaning as any other digit. That's why you have to tell explicitly where you want to stop.
If you want to remove all trailing zeros automatically, you can try:
def format_e(n):
a = '%E' % n
return a.split('E')[0].rstrip('0').rstrip('.') + 'E' + a.split('E')[1]
format_e(Decimal('40800000000.00000000000000'))
# '4.08E+10'
format_e(Decimal('40000000000.00000000000000'))
# '4E+10'
format_e(Decimal('40812300000.00000000000000'))
# '4.08123E+10'
Solution 2 - Python
Here's an example using the format() function:
>>> "{:.2E}".format(Decimal('40800000000.00000000000000'))
'4.08E+10'
Instead of format, you can also use f-strings:
>>> f"{Decimal('40800000000.00000000000000'):.2E}"
'4.08E+10'
Solution 3 - Python
Given your number
x = Decimal('40800000000.00000000000000')
Starting from Python 3,
'{:.2e}'.format(x)
is the recommended way to do it.
e means you want scientific notation, and .2 means you want 2 digits after the dot. So you will get x.xxE±n
Solution 4 - Python
No one mentioned the short form of the .format method:
Needs at least Python 3.6
f"{Decimal('40800000000.00000000000000'):.2E}"
(I believe it's the same as Cees Timmerman, just a bit shorter)
Solution 5 - Python
This is a consolidated list of the "Simple" Answers & Comments.
PYTHON 3
from decimal import Decimal
x = '40800000000.00000000000000'
# Converted to Float
x = Decimal(x)
# ===================================== # `Dot Format`
print("{0:.2E}".format(x))
# ===================================== # `%` Format
print("%.2E" % x)
# ===================================== # `f` Format
print(f"{x:.2E}")
# =====================================
# ALL Return: 4.08E+10
print((f"{x:.2E}") == ("%.2E" % x) == ("{0:.2E}".format(x)))
# True
print(type(f"{x:.2E}") == type("%.2E" % x) == type("{0:.2E}".format(x)))
# True
# =====================================
OR Without IMPORT's
# NO IMPORT NEEDED FOR BASIC FLOATS
y = '40800000000.00000000000000'
y = float(y)
# ===================================== # `Dot Format`
print("{0:.2E}".format(y))
# ===================================== # `%` Format
print("%.2E" % y)
# ===================================== # `f` Format
print(f"{y:.2E}")
# =====================================
# ALL Return: 4.08E+10
print((f"{y:.2E}") == ("%.2E" % y) == ("{0:.2E}".format(y)))
# True
print(type(f"{y:.2E}") == type("%.2E" % y) == type("{0:.2E}".format(y)))
# True
# =====================================
Comparing
# =====================================
x
# Decimal('40800000000.00000000000000')
y
# 40800000000.0
type(x)
# <class 'decimal.Decimal'>
type(y)
# <class 'float'>
x == y
# True
type(x) == type(y)
# False
x
# Decimal('40800000000.00000000000000')
y
# 40800000000.0
So for Python 3, you can switch between any of the three for now.
My Fav:
print("{0:.2E}".format(y))
Solution 6 - Python
See tables from Python string formatting to select the proper format layout. In your case it's %.2E.
Solution 7 - Python
My decimals are too big for %E so I had to improvize:
def format_decimal(x, prec=2):
tup = x.as_tuple()
digits = list(tup.digits[:prec + 1])
sign = '-' if tup.sign else ''
dec = ''.join(str(i) for i in digits[1:])
exp = x.adjusted()
return '{sign}{int}.{dec}e{exp}'.format(sign=sign, int=digits[0], dec=dec, exp=exp)
Here's an example usage:
>>> n = decimal.Decimal(4.3) ** 12314
>>> print format_decimal(n)
3.39e7800
>>> print '%e' % n
inf
Solution 8 - Python
This worked best for me:
import decimal
'%.2E' % decimal.Decimal('40800000000.00000000000000')
# 4.08E+10
Solution 9 - Python
To convert a Decimal to scientific notation without needing to specify the precision in the format string, and without including trailing zeros, I'm currently using
def sci_str(dec):
return ('{:.' + str(len(dec.normalize().as_tuple().digits) - 1) + 'E}').format(dec)
print( sci_str( Decimal('123.456000') ) ) # 1.23456E+2
To keep any trailing zeros, just remove the normalize().
Solution 10 - Python
I prefer Python 3.x way.
cal = 123.4567
print(f"result {cal:.4E}")
4 indicates how many digits are shown shown in the floating part.
cal = 123.4567
totalDigitInFloatingPArt = 4
print(f"result {cal:.{totalDigitInFloatingPArt}E} ")
Solution 11 - Python
Here is the simplest one I could find.
format(40800000000.00000000000000, '.2E')
#'4.08E+10'
('E' is not case sensitive. You can also use '.2e')
Solution 12 - Python
def formatE_decimal(x, prec=2):
""" Examples:
>>> formatE_decimal('0.1613965',10)
'1.6139650000E-01'
>>> formatE_decimal('0.1613965',5)
'1.61397E-01'
>>> formatE_decimal('0.9995',2)
'1.00E+00'
"""
xx=decimal.Decimal(x) if type(x)==type("") else x
tup = xx.as_tuple()
xx=xx.quantize( decimal.Decimal("1E{0}".format(len(tup[1])+tup[2]-prec-1)), decimal.ROUND_HALF_UP )
tup = xx.as_tuple()
exp = xx.adjusted()
sign = '-' if tup.sign else ''
dec = ''.join(str(i) for i in tup[1][1:prec+1])
if prec>0:
return '{sign}{int}.{dec}E{exp:+03d}'.format(sign=sign, int=tup[1][0], dec=dec, exp=exp)
elif prec==0:
return '{sign}{int}E{exp:+03d}'.format(sign=sign, int=tup[1][0], exp=exp)
else:
return None
Solution 13 - Python
Adding an updated answer to show how to apply e notation to small numbers only
value = 0.1
a = "{:,}".format(value) if value >= 0.001 else "{:,.3e}".format(value)
print(a) # 0.1
value = 0.00002488
a = "{:,}".format(value) if value >= 0.001 else "{:,.3e}".format(value)
print(a) # 2.488e-05