Python complex() Function

Converts a string or number to a complex number


The complex() function creates a complex number when real and imaginary parts are specified.

It can also convert a string to a complex number.

The complex number is returned in the form of real + imaginary, where the imaginary part is followed by a j.



Python complex() function parameters
realOptionalThe real part of the complex number.
Default is 0.
imaginaryOptionalThe imaginary part of the complex number.
Default is 0.

Creating Complex Numbers

You can create a complex number by specifying real and imaginary parts.


x = complex(3, 2)
print(x)	# (3+2j)
x = complex(-3, 2)
print(x)	# (-3+2j)
x = complex(3, -2)
print(x)	# (3-2j)

If you omit one of the arguments, it is assumed as 0, as default value of real and imaginary parameters is 0.


# omit imaginary part
x = complex(3)
print(x)	# (3+0j)
# omit real part
x = complex(0, 4)
print(x)	# 4j
# omit both
x = complex()
print(x)	# 0j

Convert a String to a Complex Number

You can convert a string to a complex number by specifying the first parameter as a string like '3+4j'.

When this is the case, the second parameter should be omitted.

Example: Convert a string ‘3+4j’ to a complex number

x = complex('3+4j')
print(x)	# (3+4j)

When converting from a string, the string must not contain whitespace around the central + or – operator. Otherwise, the function raises ValueError.


# ValueError: complex() arg is a malformed string
x = complex('3 + 4j')