Python内置函数complex的详细知识介绍

Python内置函数complex的详细知识介绍

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 like int and float. 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 ValueError.

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)
 

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