Are complex numbers a supported data-type in Python? If so, how do you use them?
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3 Answers
In python, you can put ‘j’ or ‘J’ after a number to make it imaginary, so you can write complex literals easily:
>>> 1j
1j
>>> 1J
1j
>>> 1j * 1j
(-1+0j)
The ‘j’ suffix comes from electrical engineering, where the variable ‘i’ is usually used for current. (Reasoning found here.)
The type of a complex number is complex, and you can use the type as a constructor if you prefer:
>>> complex(2,3)
(2+3j)
A complex number has some built-in accessors:
>>> z = 2+3j
>>> z.real
2.0
>>> z.imag
3.0
>>> z.conjugate()
(2-3j)
Several built-in functions support complex numbers:
>>> abs(3 + 4j)
5.0
>>> pow(3 + 4j, 2)
(-7+24j)
The standard module cmath has more functions that handle complex numbers:
>>> import cmath
>>> cmath.sin(2 + 3j)
(9.15449914691143-4.168906959966565j)
3 Comments
jvriesem
'i' is also used by mathematicians, physicists, and nearly all other scientists. If that isn't confusing enough, some use 'i' to represent the "positive" square root of one, whereas 'j' is the "negative" square root of one. Thus i == -j. FYJ...
joseville
@jvriesem "the positive square root of one" is one. Do you mean they use
i to represent the positive square root of negative one? and j to represent the negative square root of negative one?
copper.hat
The i/j argument for current is a bit weak, j is used for current density.
The following example for complex numbers should be self explanatory including the error message at the end
>>> x=complex(1,2)
>>> print x
(1+2j)
>>> y=complex(3,4)
>>> print y
(3+4j)
>>> z=x+y
>>> print x
(1+2j)
>>> print z
(4+6j)
>>> z=x*y
>>> print z
(-5+10j)
>>> z=x/y
>>> print z
(0.44+0.08j)
>>> print x.conjugate()
(1-2j)
>>> print x.imag
2.0
>>> print x.real
1.0
>>> print x>y
Traceback (most recent call last):
File "<pyshell#149>", line 1, in <module>
print x>y
TypeError: no ordering relation is defined for complex numbers
>>> print x==y
False
>>>
Comments
Yes, complex type is supported in Python.
For numbers, Python 3 supports 3 types int, float and complex types as shown below:
print(type(100), isinstance(100, int))
print(type(100.23), isinstance(100.23, float))
print(type(100 + 2j), isinstance(100 + 2j, complex))
Output:
<class 'int'> True
<class 'float'> True
<class 'complex'> True
For numbers, Python 2 supperts 4 types int, long, float and complex types as shown below:
print(type(100), isinstance(100, int))
print(type(10000000000000000000), isinstance(10000000000000000000, long))
print(type(100.23), isinstance(100.23, float))
print(type(100 + 2j), isinstance(100 + 2j, complex))
Output:
(<type 'int'>, True)
(<type 'long'>, True)
(<type 'float'>, True)
(<type 'complex'>, True)
answered Nov 24, 2022 at 3:18
Super Kai - Kazuya Ito
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help(complex)doesn't show any examples, unlike e.g. ` import decimal; help(decimal)`