complex 创建复数
内置函数（类）complex，Python 官方文档描述如下：
help(complex)
Help on class complex in module builtins:
class complex(object)
| complex(real=0, imag=0)
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| Create a complex number from a real part and an optional imaginary part.
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| This is equivalent to (real + imag*1j) where imag defaults to 0.
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| Methods defined here:
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| __abs__(self, /)
| abs(self)
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| __add__(self, value, /)
| Return self+value.
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| __bool__(self, /)
| self != 0
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| __divmod__(self, value, /)
| Return divmod(self, value).
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| __eq__(self, value, /)
| Return self==value.
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| __float__(self, /)
| float(self)
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| __floordiv__(self, value, /)
| Return self//value.
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| __format__(...)
| complex.__format__() -> str
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| Convert to a string according to format_spec.
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| __ge__(self, value, /)
| Return self>=value.
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| __getattribute__(self, name, /)
| Return getattr(self, name).
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| __getnewargs__(...)
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| __gt__(self, value, /)
| Return self>value.
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| __hash__(self, /)
| Return hash(self).
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| __int__(self, /)
| int(self)
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| __le__(self, value, /)
| Return self<=value.
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| __lt__(self, value, /)
| Return self<value.
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| __mod__(self, value, /)
| Return self%value.
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| __mul__(self, value, /)
| Return self*value.
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| __ne__(self, value, /)
| Return self!=value.
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| __neg__(self, /)
| -self
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| __pos__(self, /)
| +self
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| __pow__(self, value, mod=None, /)
| Return pow(self, value, mod).
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| __radd__(self, value, /)
| Return value+self.
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| __rdivmod__(self, value, /)
| Return divmod(value, self).
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| __repr__(self, /)
| Return repr(self).
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| __rfloordiv__(self, value, /)
| Return value//self.
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| __rmod__(self, value, /)
| Return value%self.
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| __rmul__(self, value, /)
| Return value*self.
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| __rpow__(self, value, mod=None, /)
| Return pow(value, self, mod).
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| __rsub__(self, value, /)
| Return value-self.
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| __rtruediv__(self, value, /)
| Return value/self.
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| __sub__(self, value, /)
| Return self-value.
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| __truediv__(self, value, /)
| Return self/value.
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| conjugate(...)
| complex.conjugate() -> complex
|
| Return the complex conjugate of its argument. (3-4j).conjugate() == 3+4j.
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| ----------------------------------------------------------------------
| Static methods defined here:
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| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| ----------------------------------------------------------------------
| Data descriptors defined here:
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| imag
| the imaginary part of a complex number
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| real
| the real part of a complex number
返回值为 real + imag*1j 的复数，或将字符串或数字转换为复数。
- 如果第一个形参是字符串，则它被解释为一个复数，并且函数调用时必须没有第二个形参。
- 第二个形参不能是字符串。
- 每个实参都可以是任意的数值类型（包括复数）。
- 如果省略了 imag，则默认值为零，构造函数会像 int 和 float 一样进行数值转换。
- 如果两个实参都省略，则返回 0j。
- 当从字符串转换时，字符串在 + 或 - 的周围必须不能有空格。
type(complex)
type
complex('1')
(1+0j)
complex('1+2j')
(1+2j)
complex(1j, 2j)
(-2+1j)
complex(1j)
1j
complex()
0j
complex('1 + 2j')
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-7-fd0fa4b53d7c> in <module>
----> 1 complex('1 + 2j')
ValueError: complex() arg is a malformed string