Python 內建函數complex詳解

英文文檔：

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.

說明：

　　1. 函數功能，返回一個複數。有兩個選擇性參數。

　　2. 當兩個參數都不提供時，返回複數 0j。

>>> complex()0j 

　　3. 當第一個參數為字串時，調用時不能提供第二個參數。此時字串參數，需是一個能表示複數的字串，而且加號或者減號左右不能出現空格。

>>> complex('1+2j',2) #第一個參數為字串，不能接受第二個參數Traceback (most recent call last): File "", line 1, in   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 "", line 1, in   complex('1 + 2j')ValueError: complex() arg is a malformed string

　　4. 當第一個參數為int或者float時，第二個參數可為空白，表示虛部為0；如果提供第二個參數，第二個參數也需為int或者float。

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

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