Python complex()

Python complex() function is used to create complex numbers. It’s a built-in function that returns a complex type from the input parameters.

Python complex() function syntax is:


class complex([real[, imag]])

Some of the important points to remember while using complex() function are:

Python complex() function returns complex number with value real + imag*1j.
We can convert string to complex number using complex() function. If the first argument is string, second argument is not allowed.
While converting string to complex number, whitespaces in string is not allowed. For example, ‘1+2j’ is fine but ‘1 + 2j’ is not.
If no argument is passed, then 0j is returned.
Input arguments can be in any numeric format such as hexadecimal, binary etc.
Underscores in numeric literals are also allowed from Python 3.6 onwards, refer PEP 515.

Python complex() examples

Let’s look at some complex() function examples.


c = complex()
print(type(c))
print(c)

Output:


<class 'complex'>
0j


c = complex(1, 1)
print(c)

c = complex(1.5, -2.1)
print(c)

c = complex(0xF)  # hexadecimal
print(c)

c = complex(0b1010, -1)  # binary
print(c)

Output:


(1+1j)
(1.5-2.1j)
(15+0j)
(10-1j)


c = complex(10_000_000.0, -2)
print(c)

Output: (10000000-2j)


c = 1 + 2j
c = complex(c, -4)
print(c)
c = complex(1+2j, 1+2J)
print(c)

Output:


(1-2j)
(-1+3j)

Notice how complex literals are combined to form a new complex number. If the second argument is a complex number, then the calculation is different.


c = complex("1+2j")
print(c)

Output: (1+2j)

Let’s see what happens when the input string has white spaces.


c = complex("1 + 2j")

Output: ValueError: complex() arg is a malformed string

Let’s see what happens when the first argument is a string and the second argument is also provided.


c = complex("1+j", 2)

Output: TypeError: complex() can't take second arg if first is a string

What if we try to pass the second argument as String, let’s see what error we get.


c = complex(2, "-2j")

Output: TypeError: complex() second arg can't be a string

That’s all for python complex() function.

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