CODEWITHSUNDEEP
pythonpython-2.7numpy
prashantgpt91
prashantgpt91

Reputation: 1795

Python code not running

I am working with this tutorial. On the example

import csv as csv

import numpy as np

csv_file_object = csv.reader(open('train.csv', 'rb'))

header = csv_file_object.next()

data = []

for row in csv_file_object:

data.append(row)

data = np.array(data)

I encountered the following error:

Traceback (most recent call last):

File "C:/Users/Prashant/Desktop/data mining/demo.py", line 7,

in module data.append(row)

AttributeError: 'numpy.ndarray' object has no attribute 'append'

I googled this and found this question/answer on append, but I didn't get anything.

Upvotes: 0

Views: 5495

Answers (3)

Serial
Serial

Reputation: 8043

Well, looking at the link to the other question you asked, it looks like numpy.ndarray has no attribute called append, but it looks like NumPy does.

So instead use:

numpy.append()

Or you can try to concatenate.

Take a look at Stack Overflow question Append a NumPy array to a NumPy array.

Upvotes: 0

moooeeeep
moooeeeep

Reputation: 32542

Have a look at the example at the linked location:

#The first thing to do is to import the relevant packages
# that I will need for my script, 
#these include the Numpy (for maths and arrays)
#and csv for reading and writing csv files
#If i want to use something from this I need to call 
#csv.[function] or np.[function] first

import csv as csv 
import numpy as np

#Open up the csv file in to a Python object
csv_file_object = csv.reader(open('../csv/train.csv', 'rb')) 
header = csv_file_object.next()  #The next() command just skips the 
                                 #first line which is a header
data=[]                          #Create a variable called 'data'
for row in csv_file_object:      #Run through each row in the csv file
    data.append(row)             #adding each row to the data variable
data = np.array(data)            #Then convert from a list to an array
                                 #Be aware that each item is currently
                                 #a string in this format

Python is indentation-sensitive. That is, the indentation level will determine the body of the for loop, and according to the comment by thegrinner:

There is a HUGE difference in whether your data = np.array(data) line is in the loop or outside it.

That being said the following should demonstrate the difference:

>>> import numpy as np
>>> data = []
>>> for i in range(5):
...     data.append(i)
... 
>>> data = np.array(data) # re-assign data after the loop
>>> print data
array([0, 1, 2, 3, 4])

vs.

>>> data = []
>>> for i in range(5):
...     data.append(i)
...     data = np.array(data) # re-assign data within the loop
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
AttributeError: 'numpy.ndarray' object has no attribute 'append'

As a side-note, I'd doubt the quality of the tutorial you are apparantly following is appropriate for bloody Python starters. I think this more basic (official) tutorial should be more appropriate for a quick first overview of the language: http://docs.python.org/2/tutorial/

Upvotes: 1

thegrinner
thegrinner

Reputation: 12241

Check your indentation. If data = np.array(data) is in your for loop (ie indented the same amount as data.append(row)), you'll turn data into a Numpy array before you've finished appending items to a list.

This will cause the error you see because lists have an append() method, while numpy arrays do not. Your for loop should look something like

data = [] # Make data a list 
for row in csv_file_object: #iterate through rows in the csv and append them to the list
    data.append(row)

# Turn the list into an array. Notice this is NOT indented! If it is, the data
# list will be overwritten!
data = np.array(data)

Check Dive Into Python for a more extensive explanation of how indentation works in Python.

Upvotes: 0

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