1 ,nd 結構 : 幾行幾列 ( nd01.shape )
代碼 :
if __name__ == '__main__' :
nd01 = np. genfromtxt( "world_alcohol.txt" , skip_header= 1 , delimiter= "," )
res = nd01. shape
print ( res)
== == == == == == == == == == =
( 997 , 5 )
2 ,nd 計算 :作用於每個元素 ( nd02 = nd01 + 1 )
nd 的計算不僅對一個元素生效,對每個元素都生效
代碼 :
if __name__ == '__main__' :
nd01 = np. genfromtxt( "aa.txt" , delimiter= "," )
nd02 = nd01 + 1
print ( nd01)
print ( nd02)
== == == == == == == == == == == == == =
[ [ 1 . 2 . 3 . 4 . 5 . ]
[ 6 . 7 . 8 . 9 . 0 . ] ]
[ [ 2 . 3 . 4 . 5 . 6 . ]
[ 7 . 8 . 9 . 10 . 1 . ] ]
3 ,nd 計算 : 布爾類型
nd01 = np. genfromtxt( "aa.txt" , delimiter= "," )
nd02 = ( nd01 == 5 )
print ( nd01)
print ( nd02)
== == == == == == == == == == == == == == =
[ [ 1 . 2 . 3 . 4 . 5 . ]
[ 6 . 7 . 8 . 9 . 0 . ] ]
[ [ False False False False True ]
[ False False False False False ] ]
4 ,取特定值 : 將偶數取出來 【nd02 = nd01[nd01%2 == 0]】
得到 : 一維 nd
if __name__ == '__main__' :
nd01 = np. genfromtxt( "aa.txt" , delimiter= "," )
nd02 = nd01[ nd01% 2 == 0 ]
print ( nd01)
print ( nd02)
== == == == == == == == == == == == =
[ [ 1 . 2 . 3 . 4 . 5 . ]
[ 6 . 7 . 8 . 9 . 0 . ] ]
== == == == == == == == == == == == =
[ 2 . 4 . 6 . 8 . 0 . ]
5 ,取特定值 : 原理 ( True 被選了出來 )
原理 : True 爲天選之子
代碼 :
if __name__ == '__main__' :
nd01 = np. array( [ 1 , 2 , 3 , 4 , 5 ] )
nd02 = np. array( [ True , False , True , False , False ] )
nd03 = nd01[ nd02]
print ( nd01)
print ( nd02)
print ( nd03)
== == == == == == == == == == == == =
[ 1 2 3 4 5 ]
[ True False True False False ]
[ 1 3 ]
6 ,取特定值 : 第二個字段是偶數的行
目的 : 將第二個值是匹數的行找出來
代碼 :
if __name__ == '__main__' :
nd01 = np. genfromtxt( "aa.txt" , delimiter= "," )
nd02 = nd01[ : , 1 ] % 2 == 0
nd03 = nd01[ nd02]
print ( nd01)
print ( nd02)
print ( nd03)
== == == == == == == == == == == == == == == ==
[ [ 1 . 2 . 3 . 4 . 5 . ]
[ 6 . 7 . 8 . 9 . 0 . ]
[ 3 . 2 . 4 . 6 . 5 . ] ]
== == == == == == == == == == == == == == == ==
[ True False True ]
== == == == == == == == == == == == == == == ==
[ [ 1 . 2 . 3 . 4 . 5 . ]
[ 3 . 2 . 4 . 6 . 5 . ] ]