complex() Complex number
Last updated: 2026-09-22
complex() Complex number
complex() builds a complex number as real + imag*j; with no args returns 0j.
| Category | Built-in Functions |
|---|---|
| Kind | Built-in Function |
| Python Version | all |
📝 Syntax
complex([real[, imag]])⚙️ Parameters
| real Optional | Real part: a number or numeric string.（Default：None） |
|---|---|
| imag Optional | Imaginary part (numeric).（Default：None） |
Returns：complex. real + imag*j; 0j when called with no arguments.
💥 Raises
TypeError— Raised when an argument cannot be converted to complex.ValueError— Raised when a string cannot be parsed as a complex number.
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
(3+4j)
(1+2j)
(5+0j)💡 Related Cases
More case studies coming soon — check back later.
❓ FAQ
QWhat does complex() return with no arguments?
AIt returns 0j, a complex number whose real and imaginary parts are both 0.
QIs there a difference between complex('1+2j') and complex(1, 2)?
AThe results are the same (both are (1+2j)). But the string form cannot contain spaces ('1 + 2j' raises a ValueError), and you cannot pass both a string and an imag argument.
QWhat is the result of complex(5)?
AIt returns 5+0j; with a single argument, the imaginary part defaults to 0.
QHow do I extract the real and imaginary parts of a complex number?
AUse the .real and .imag attributes, e.g. (3+4j).real returns 3.0 and .imag returns 4.0; use abs() for the magnitude.
