Detailed explanation of Python built-in function complex-Python Tutorial-php.cn

Detailed explanation of Python built-in function complex

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Release： 2016-12-05 13:27:13

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English document:

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.

Instructions:

　1. Function function, returns a complex number. There are two optional parameters.

　2. When neither parameter is provided, the complex number 0j is returned.

>>> complex()
0j

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　3. When the first parameter is a string, the second parameter cannot be provided when calling. At this time, the string parameter must be a string that can represent a plural number, and there must be no spaces around the plus or minus sign.

>>> 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

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4. When the first parameter is int or float, the second parameter can be empty, indicating that the imaginary part is 0; if the second parameter is provided, the second parameter must also be int or float.

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

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