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.
Answers:
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Method 1
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'
Method 2
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'
Method 3
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
Method 4
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)
Method 5
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))
Method 6
See tables from Python string formatting to select the proper format layout. In your case it’s %.2E.
Method 7
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
Method 8
This worked best for me:
import decimal
'%.2E' % decimal.Decimal('40800000000.00000000000000')
# 4.08E+10
Method 9
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().
Method 10
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} ")
Method 11
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’)
Method 12
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
Method 13
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
All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0