Is there a pythonic way of splitting a number such as 1234.5678 into two parts (1234, 0.5678) i.e. the integer part and the decimal part?
Splitting a number into the integer and decimal parts
Viewed 182803
9 Answers
I have come up with two statements that can divide positive and negative numbers into integer and fraction without compromising accuracy (bit overflow) and speed.
As an example, a positive or negative value of the value 100.1323 will be divided as:
100.1323 -> (100, 0.1323)
-100.1323 -> (-100, -0.1323)
Code
# Divide a number (x) into integer and fraction
i = int(x) # Get integer
f = (x*1e17 - i*1e17) / 1e17 # Get fraction
Speedtest
The performance test shows that the two statements are faster than math.modf, as long as they are not put into their own function or method.
test.py:
#!/usr/bin/env python
import math
import cProfile
""" Get the performance of both statements and math.modf """
X = -100.1323 # The number to be divided into integer and fraction
LOOPS = range(5 * 10 ** 6) # Number of loops
def scenario_a():
""" Get the performance of the statements """
for _ in LOOPS:
i = int(X) # -100
f = (X*1e17-i*1e17)/1e17 # -0.1323
def scenario_b():
""" Tests the speed of the statements when integer need to be float.
NOTE: The only difference between this and math.modf is the accuracy """
for _ in LOOPS:
i = int(X) # -100
i, f = float(i), (X*1e17-i*1e17)/1e17 # (-100.0, -0.1323)
def scenario_c():
""" Tests the speed of the statements in a function """
def modf(x):
i = int(x)
return i, (x*1e17-i*1e17)/1e17
for _ in LOOPS:
i, f = modf(X) # (-100, -0.1323)
def scenario_d():
""" Tests the speed of math.modf """
for _ in LOOPS:
f, i = math.modf(X) # (-0.13230000000000075, -100.0)
def scenario_e():
""" Tests the speed of math.modf when the integer part should be integer """
for _ in LOOPS:
f, i = math.modf(X) # (-0.13230000000000075, -100.0)
i = int(i) # -100
if __name__ == '__main__':
cProfile.run('scenario_a()')
cProfile.run('scenario_b()')
cProfile.run('scenario_c()')
cProfile.run('scenario_d()')
cProfile.run('scenario_e()')
Result:
4 function calls in 1.357 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 1.357 1.357 <string>:1(<module>)
1 1.357 1.357 1.357 1.357 test.py:11(scenario_a)
1 0.000 0.000 1.357 1.357 {built-in method builtins.exec}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
4 function calls in 1.858 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 1.858 1.858 <string>:1(<module>)
1 1.858 1.858 1.858 1.858 test.py:18(scenario_b)
1 0.000 0.000 1.858 1.858 {built-in method builtins.exec}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
5000004 function calls in 2.744 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 2.744 2.744 <string>:1(<module>)
1 1.245 1.245 2.744 2.744 test.py:26(scenario_c)
5000000 1.499 0.000 1.499 0.000 test.py:29(modf)
1 0.000 0.000 2.744 2.744 {built-in method builtins.exec}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
5000004 function calls in 1.904 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 1.904 1.904 <string>:1(<module>)
1 1.073 1.073 1.904 1.904 test.py:37(scenario_d)
1 0.000 0.000 1.904 1.904 {built-in method builtins.exec}
5000000 0.831 0.000 0.831 0.000 {built-in method math.modf}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
5000004 function calls in 2.547 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 2.547 2.547 <string>:1(<module>)
1 1.696 1.696 2.547 2.547 test.py:43(scenario_e)
1 0.000 0.000 2.547 2.547 {built-in method builtins.exec}
5000000 0.851 0.000 0.851 0.000 {built-in method math.modf}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
Use C/C++ extension
I have tried to compile the two statements with C/C++ support and the result was even better. With Python extension module it was possible to get a method that was faster and more accurate than math.modf.
math2.pyx:
def modf(number):
cdef float num = <float> number
cdef int i = <int> num
return i, (num*1e17 - i*1e17) / 1e17
See Basics of Cython
test.py:
#!/usr/bin/env python
import math
import cProfile
import math2
""" Get the performance of both statements and math.modf """
X = -100.1323 # The number to be divided into integers and fractions
LOOPS = range(5 * 10 ** 6) # Number of loops
def scenario_a():
""" Tests the speed of the statements in a function using C/C++ support """
for _ in LOOPS:
i, f = math2.modf(X) # (-100, -0.1323)
def scenario_b():
""" Tests the speed of math.modf """
for _ in LOOPS:
f, i = math.modf(X) # (-0.13230000000000075, -100.0)
if __name__ == '__main__':
cProfile.run('scenario_a()')
cProfile.run('scenario_b()')
Result:
5000004 function calls in 1.629 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 1.629 1.629 <string>:1(<module>)
1 1.100 1.100 1.629 1.629 test.py:10(scenario_a)
1 0.000 0.000 1.629 1.629 {built-in method builtins.exec}
5000000 0.529 0.000 0.529 0.000 {math2.modf}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
5000004 function calls in 1.802 seconds
Ordered by: standard name
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 1.802 1.802 <string>:1(<module>)
1 1.010 1.010 1.802 1.802 test.py:16(scenario_b)
1 0.000 0.000 1.802 1.802 {built-in method builtins.exec}
5000000 0.791 0.000 0.791 0.000 {built-in method math.modf}
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
NOTE
The statements can be faster with modulo, but modulo can not be used to split negative numbers into integer and fraction parts.
i, f = int(x), x*1e17%1e17/1e17 # Divide a number (x) into integer and fraction
As an example, a positive or negative value of the value 100.1323 will be divided as:
100.1323 -> (100, 0.1323)
-100.1323 -> (-100, 0.8677) <-- Wrong
This will accomplish the task without the issue of dropping leading zeroes (like holydrinker's answer):
Code
def extract_int_decimal():
'''get the integer and decimal parts of a given number
by converting it to string and using split method
'''
num = 1234.5678
split_num = str(num).split('.')
int_part = int(split_num[0])
decimal_part = int(split_num[1]) * 10 ** -len(split_num[1])
print("integer part:",int_part)
print("decimal part:",decimal_part)
extract_int_decimal()
Result
integer part: 1234
decimal part: 0.5678000000000001
Related