Python内置函数(13)――complex

英文文档： class complex ( [ real [, imag ] ] )

Return a complex number with the value real + imag *1j or convert a string or number to a complex number. If the first parameter is a string, it will be interpreted as a complex number and the function must be called without a second parameter. The second parameter can never be a string. Each argument may be any numeric type (including complex). If imag is omitted, it defaults to zero and the constructor serves as a numeric conversion likeand. If both arguments are omitted, returns 0j .

Note

When converting from a string, the string must not contain whitespace around the central + or - operator. For example, complex('1+2j') is fine, but complex('1 + 2j') raises.

说明：

1. 函数功能，返回一个复数。有两个可选参数。

2. 当两个参数都不提供时，返回复数 0j。

>>> complex() 0j

3. 当第一个参数为字符串时，调用时不能提供第二个参数。此时字符串参数，需是一个能表示复数的字符串，而且加号或者减号左右不能出现空格。

>>> complex('1+2j',2) #第一个参数为字符串，不能接受第二个参数 Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> complex('1+2j',2) TypeError: complex() can't take second arg if first is a string >>> complex('1 + 2j') #不能有空格 Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> complex('1 + 2j') ValueError: complex() arg is a malformed string

4. 当第一个参数为int或者float时，第二个参数可为空，表示虚部为0；如果提供第二个参数，第二个参数也需为int或者float。

>>> complex(2) (2+0j) >>> complex(2.1,-3.4) (2.1-3.4j)