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()

Python complex() function syntax is:

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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.

complex() without any argument

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

Output:

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<class 'complex'>
0j

complex() with numeric arguments

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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:

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

complex() with underscore numeric literals

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

Output: (10000000-2j)

complex() with complex number inputs

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

Output:

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(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.

complex() with string arguments

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

Output: (1+2j)

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

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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.

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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.

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

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

That’s all for python complex() function.

Reference: Official Documentation

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