PythonError: 'float' object is not iterable

Question

I'm trying to do 3 slices from a list of vectors from a txt file, with 2 columns, using conditions to separate the RGB.

But when I run the program the following error appears: "'float' object is not iterable". Can anyone help me?

#File opening
arq = open('arquivo.txt','r')

lines = arq.readlines()
arq.close()

vetor_x = []
vetor_y = []
lista_geral = []

for line in lines:
    line = line.replace('\n','')
    line = line.strip()
    line = line.replace(',','.')
    line = line.split('\t')

    if(len(line) == 2):
        X = line[0]
        Y = line[1]
        vetor_x.append(float(X))
        vetor_y.append(float(Y))
        lista_geral.append([X,Y])

#Conditions
B = 0
G = 0
R = 0

for i in range(0,len(vetor_x)):

    if vetor_x[i] <= 500:
        vetor_xB[B] = list(vetor_x[i])
        vetor_yB[B] = list(vetor_y[i])
        B += 1

    elif vetor_x[i] <= 600:
        vetor_xG[G] = list(vetor_x[i])
        vetor_yG[G] = list(vetor_y[i])
        G += 1

    elif vetor_x[i] <= 700:
        vetor_xR[R] = list(vetor_x[i])
        vetor_yR[R] = list(vetor_y[i])
        R += 1

print('####### vetor_xB #######')
print(vetor_xB)
print('####### vetor_yB #######')
print(vetor_yB)
print('####### vetor_xG #######')
print(vetor_xG)
print('####### vetor_yG #######')
print(vetor_yG)
print('####### vetor_xR #######')
print(vetor_xR)
print('####### vetor_yR #######')
print(vetor_yR)

However, when I try to run it, this causes this error:

Traceback (most recent call last):
  File "teste4.py", line 30, in <module>
    vetor_xB[B] = list(vetor_x[i])
TypeError: 'float' object is not iterable

Please help me!

Answer 1

vetor_x is definitely iterable as shown when you define it in line 6. That leaves vetor_xB as the source of your error. I do not see it defined anywhere.

From your usage of vetor_xB, you could define it as a dictionary somewhere before your loop and call vetor_xB.values() to output your desired list.

Alternatively (and preferably), you can define vetor_xB as a list and instead of vetor_xB[B] you can write vetor_xB.append(B). This seems the simpler, more logical solution.

And even more preferably use pandas as below. This is a much quicker, more efficient solution and honestly removes much of the time taken to manually parse your data. Here entire document is replaced with 6 lines of code + some print statements. It might not be the most memory efficient, but it offers some significant advantages that I think are worth the switch.

df = pd.read_csv(archive_path, sep='   ', header=None)

for col in df.columns: df[col] = pd.to_numeric(df[col].str.replace(',','.'))

df.columns = ['X', 'Y']

vetores = {}
vetores['vetor_B'] = df.loc[df['X']<=500]
vetores['vetor_G'] = df.loc[(df['X']>500) & df['X']<=600]
vetores['vetor_R'] = df.loc[(df['X']>600) & df['X']<=700]

for vetor in vetores.keys():
    print(vetor+'X:')
    print(vetores[vetor]['X'])
    print(vetor+'Y:')
    print(vetores[vetor]['Y'])
    print('-'*40)

Answer 2

The error means that this line vetor_xB[B] = list(vetor_x[i]), is not able to convert the float values to a list, instead you probably want to simply append the float values to your lists, but we need to define those lists before we can use them, like this:

# Define the lists we want to append the data to
vetor_xB = []
vetor_yB = []
vetor_xG = []
vetor_yG = []
vetor_xR = []
vetor_yR = []

for i in range(len(vetor_x)):
    if vetor_x[i] <= 500:
        vetor_xB.append(vetor_x[i])
        vetor_yB.append(vetor_y[i])

    elif vetor_x[i] <= 600:
        vetor_xG.append(vetor_x[i])
        vetor_yG.append(vetor_y[i])

    elif vetor_x[i] <= 700:
        vetor_xR.append(vetor_x[i])
        vetor_yR.append(vetor_y[i])

Then your output should be as you expect:

####### vetor_xB #######
[400.0, 401.10373, 409.54288, 425.24905, 442.71341, 470.96112, 488.7771, 499.79489, 499.91208, 500.0]
####### vetor_yB #######
[46.5713, 42.8136, 103.12, 12.6044, 262.43, 680.958, 171.28, 39.846, 41.1616, 39.2299]
####### vetor_xG #######
[523.70581, 540.81854, 579.26355, 593.3288, 600.0]
####### vetor_yG #######
[38523.1, 31554.2, 243.866, 90.6795, 212.789]
####### vetor_xR #######
[602.58838, 618.64624, 630.01563, 655.33307, 669.74994, 686.74548, 698.11487, 700.0]
####### vetor_yR #######
[251.602, 367.089, 3568.19, 44230.4, 7747.32, 768.864, 1229.72, 1808.8]

Note: Formatting of reading the file can be simplified, replace all of this:

for line in lines:
    line = line.replace('\n','')
    line = line.strip()
    line = line.replace(',','.')
    line = line.split('\t')

with just these 3 lines:

for line in lines:
    line = line.replace(',','.')
    line = line.strip().split()

Answer 3

In this code

if vetor_x[i] <= 500:
    vetor_xB[B] = list(vetor_x[i])

it is clear from your if-test that you expect vetor_x[i] to be a number; and it is a number, because otherwise you would get a runtime error on the if-test.

But then you are calling list() on this number. So I suspect that list(x) does not do what you think it does. What it actually does is take all the elements of x (which could be a list or a tuple or a string or ...) and put them in a list. Suppose vetor_x[i] == 400.00000. Then your code is doing list(400.00000). That makes no sense.

I think you may intend

if vetor_x[i] <= 500:
    vetor_xB.append(vetor_x[i])

...but that is just a guess.

You can't make a Python list longer by assigning values to elements that don't exist. So if vetor_xB is an empty list, then assigning vetor_xB[B] = will fail, because irrespective of the value of B, there is no element B: if B == 0 then vetor_xB[B] is the same as vetor_xB[0], and trying to assign that will fail because there is no element zero.

So, to make the list longer, use append() instead. But to append to a list, the list must first exist. Your code doesn't provide a starting value for vetor_xB. At the top of the program there needs to be something like vetor_xB == [].