# Python complex()

Filed Under: Python

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:

``````
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

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

Output:

``````
<class 'complex'>
0j
``````

### complex() with numeric arguments

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

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

print(c)

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

Output:

``````
(1+1j)
(1.5-2.1j)
(15+0j)
(10-1j)
`````` ### complex() with underscore numeric literals

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

Output: `(10000000-2j)`

### complex() with complex number inputs

``````
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.

### complex() with string arguments

``````
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.

You can checkout complete python script and more Python examples from our GitHub Repository.

Reference: Official Documentation

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