Python Built-in Methods – Python complex() Function

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.



Parameter Condition Description
real Optional The real part of the complex number.
Default is 0.
imaginary Optional The 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)
# Prints (3+2j)

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

x = complex(3, -2)
# Prints (3-2j)

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

# omit imaginary part
x = complex(3)
# Prints (3+0j)

# omit real part
x = complex(0, 4)
# Prints 4j

# omit both
x = complex()
# Prints 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'. In this case the second parameter should be omitted.

# Convert a string '3+4j' to a complex number
x = complex('3+4j')
# Prints (3+4j)

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

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


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