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