在python2.7.11中,为什么我不能删除fileopen代码?
问题描述:
的.txt
文件保持数据如下(源:在2章here “datingTestSet2.txt”):在python2.7.11中,为什么我不能删除fileopen代码?
40920 8.326976 0.953952 largeDoses
14488 7.153469 1.673904 smallDoses
26052 1.441871 0.805124 didntLike
75136 13.147394 0.428964 didntLike
38344 1.669788 0.134296 didntLike
...
代码:
from numpy import *
import operator
from os import listdir
def file2matrix(filename):
fr = open(filename)
# arr = fr.readlines() # Code1!!!!!!!!!!!!!!!!!!!
numberOfLines = len(fr.readlines()) #get the number of lines in the file
returnMat = zeros((numberOfLines,3)) #prepare matrix to return
classLabelVector = [] #prepare labels return
fr = open(filename) # Code2!!!!!!!!!!!!!!!!!!!!!
index = 0
for line in fr.readlines():
line = line.strip()
listFromLine = line.split('\t')
returnMat[index,:] = listFromLine[0:3]
classLabelVector.append(int(listFromLine[-1]))
index += 1
return returnMat,classLabelVector
datingDataMat, datingLabels = file2matrix('datingTestSet2.txt')
此函数的结果是:
datingDataMat datingLabels
40920 8.326976 0.953952 3
14488 7.153469 1.673904 2
26052 1.441871 0.805124 1
75136 13.147394 0.428964 1
38344 1.669788 0.134296 1
72993 10.141740 1.032955 1
35948 6.830792 1.213192 3
42666 13.276369 0.543880 3
67497 8.631577 0.749278 1
35483 12.273169 1.508053 3
50242 3.723498 0.831917 1
... ... ... ...
我的问题是:
当我刚刚删除Code2(
fr = open(filename)
,其中index = 0
以上), 函数的结果变成全零矩阵,并且全零矢量。 为什么我不能删除Code2?不第一行(fr = open(filename)
工作?-
当我刚刚加入代码1(
arr = fr.readlines()
),这是错误的。为什么???returnMat[index,:] = listFromLine[0:3] IndexError: index 0 is out of bounds for axis 0 with size 0
答
1)无法删除由于此行的Code2行:
numberOfLines = len(fr.readlines()) #get the number of lines in the file
在该行中,您正在阅读文件的末尾。再次打开它可以让你在文件的开始处...
2)类似于上面的答案,如果你调用readLines()来读取所有行并将文件光标移动到文件...因此,如果您再次尝试在文件上读取文件,则没有任何可读的文件,因此失败。
答
您目前位于文件的末尾。因此,您第二次尝试阅读文件内容时会产生错误。你需要回到文件的开头。用途:
fr.seek(0)
您的相反:
fr = open(filename) # Code2!!!!!!!!!!!!!!!!!!!!!
答
你只需要readlines
一次。
def file2matrix(filename):
fr = open(filename)
lines = fr.readlines()
fr.close()
numberOfLines = len(lines) #get the number of lines in the file
returnMat = zeros((numberOfLines,3)) #prepare matrix to return
classLabelVector = [] #prepare labels return
index = 0
for line in lines:
line = line.strip()
listFromLine = line.split('\t')
returnMat[index,:] = listFromLine[0:3]
# careful here, returnMat is initialed as floats
# listFromLine is list of strings
classLabelVector.append(int(listFromLine[-1]))
index += 1
return returnMat,classLabelVector
我可以建议一些其他的变化:
def file2matrix(filename):
with open(filename) as f:
lines = f.readlines()
returnList = []
classLabelList = []
for line in lines:
listFromLine = line.strip().split('\t')
returnList.append(listFromLine[0:3])
classLabelList.append(int(listFromLine[-1]))
returnMat = np.array(returnList, dtype=float)
return returnMat, classLabelList
甚至
def file2matrix(filename):
with open(filename) as f:
lines = f.readlines()
ll = [line.strip().split('\t')]
returnMat = np.array([l[0:3] for l in ll], dtype=float)
classLabelList = [int(l[-1]) for l in ll]
# classLabelVec = np.array([l[-1] for l in ll], dtype=int)
return returnMat, classLabelList