Python complex() Function

Converts a string or number to a complex number

Usage

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.

Syntax

complex(real,imaginary)

Python complex() function parameters
ParameterConditionDescription
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.

Example:

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.

Example:

# 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.

Example:

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