1、在将多个以逗号分隔的值赋给一个变量时,多个值被打包成一个元组类型。当我们将一个元组赋给多个变量时,它将解包成多个值,然后分别将其赋给相应的变量。
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# 打包
a = 1 , 10 , 100
print ( type (a), a) # <class 'tuple'> (1, 10, 100)
# 解包
i, j, k = a
print (i, j, k) # 1 10 100
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2、解包时,如果解包出来的元素数目与变量数目不匹配,就会引发ValueError异常。错误信息为:too many values to unpack(解包的值太多)或not enough values to unpack(解包的值不足)。
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a = 1 , 10 , 100 , 1000
# i, j, k = a # ValueError: too many values to unpack (expected 3)
# i, j, k, l, m, n = a # ValueError: not enough values to unpack (expected 6, got 4)
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知识点扩充:
python之打包,解包
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#coding:utf-8
#字符串,列表,元组打包与解包
aString = 'abc'
aList = [ 1 , 2 , 3 ]
aTuple = 'a' , 'A' , 1
print ( 'Unpacking string......' )
first, second, third = aString
print ( "string values:" , first, second, third)
print ( '\nUnpacking list......' )
first, second, third = aList
print ( "string values:" , first, second, third)
print ( '\nUnpacking tuple......' )
first, second, third = aTuple
print ( "string values:" , first, second, third)
#swapping two values
x = 3
y = 4
print ( '\nBefore swapping: x = %d,y =%d' % (x, y))
#首先将右边的部分打包成一个元组,即(4,3),而后解包指派给变量x,y
x, y = y, x #swap Variables
print ( 'After swapping: x = %d, y = %d' % (x, y))
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