How to convert List to numpy Array

I was able to recreate your issue using the below code -

Code to recreate the issue -

import numpy as np
import tensorflow as tf
print(tf.__version__)
from tensorflow.keras.preprocessing.text import Tokenizer

label_tokenizer = Tokenizer()

# Fit on a text 
fit_text = "Tensorflow warriors are awesome people"
label_tokenizer.fit_on_texts(fit_text)

# Training Labels
train_labels = "Tensorflow warriors are great people"
training_label_list = np.array(label_tokenizer.texts_to_sequences(train_labels))

# Print the 
print(training_label_list)
print(type(training_label_list))
print(type(training_label_list[0]))

Output -

2.2.0
[list([9]) list([1]) list([10]) list([5]) list([3]) list([2]) list([11])
 list([7]) list([3]) list([6]) list([]) list([6]) list([4]) list([2])
 list([2]) list([12]) list([3]) list([2]) list([5]) list([]) list([4])
 list([2]) list([1]) list([]) list([4]) list([2]) list([1]) list([])
 list([]) list([2]) list([1]) list([4]) list([9]) list([]) list([8])
 list([1]) list([3]) list([8]) list([7]) list([1])]
<class 'numpy.ndarray'>
<class 'list'>

Solution -

1. Replacing np.array with np.hstack will fix your problem. Your model.fit() should work fine now.
2. Else if you are looking for the expected output as in your question, training_label_list = label_tokenizer.texts_to_sequences(train_labels) will give you a list of list. You can use np.array([np.array(i) for i in training_label_list]) to convert to array of array. This works only if your list of lists contains lists with same number of elements.

np.hstack Code - Code for Point number 1 in solution.

import numpy as np
import tensorflow as tf
print(tf.__version__)
from tensorflow.keras.preprocessing.text import Tokenizer

label_tokenizer = Tokenizer()

# Fit on a text 
fit_text = "Tensorflow warriors are awesome people"
label_tokenizer.fit_on_texts(fit_text)

# Training Labels
train_labels = "Tensorflow warriors are great people"
training_label_list = np.hstack(label_tokenizer.texts_to_sequences(train_labels))

# Print the 
print(training_label_list)
print(type(training_label_list))
print(type(training_label_list[0]))

Output -

2.2.0
[ 9.  1. 10.  4.  2.  3. 11.  7.  2.  5.  5.  6.  3.  3. 12.  2.  3.  4.
  6.  3.  1.  3.  1.  6.  9.  8.  1.  2.  8.  7.  1.]
<class 'numpy.ndarray'>
<class 'numpy.float64'>

Expected output as in question - Code for Point number 2 in solution.

import numpy as np
import tensorflow as tf
print(tf.__version__)
from tensorflow.keras.preprocessing.text import Tokenizer

label_tokenizer = Tokenizer()

# Fit on a text 
fit_text = "Tensorflow warriors are awesome people"
label_tokenizer.fit_on_texts(fit_text)

# Training Labels
train_labels = "Tensorflow warriors are great people"
training_label_list = label_tokenizer.texts_to_sequences(train_labels)

# Print 
print(training_label_list)
print(type(training_label_list))
print(type(training_label_list[0]))

# To convert elements to array
training_label_list = np.array([np.array(i) for i in training_label_list])

# Print
print(training_label_list)
print(type(training_label_list))
print(type(training_label_list[0]))

Output -

2.2.0
[[9], [1], [10], [4], [2], [3], [11], [7], [2], [5], [], [5], [6], [3], [3], [12], [2], [3], [4], [], [6], [3], [1], [], [], [3], [1], [6], [9], [], [8], [1], [2], [8], [7], [1]]
<class 'list'>
<class 'list'>
[array([9]) array([1]) array([10]) array([4]) array([2]) array([3])
 array([11]) array([7]) array([2]) array([5]) array([], dtype=float64)
 array([5]) array([6]) array([3]) array([3]) array([12]) array([2])
 array([3]) array([4]) array([], dtype=float64) array([6]) array([3])
 array([1]) array([], dtype=float64) array([], dtype=float64) array([3])
 array([1]) array([6]) array([9]) array([], dtype=float64) array([8])
 array([1]) array([2]) array([8]) array([7]) array([1])]
<class 'numpy.ndarray'>
<class 'numpy.ndarray'>

Hope this answers your question. Happy Learning.

Update 2/6/2020 - Anirudh_k07, As per our discussion, I had a look into your program and you are getting below error in model.fit() after using np.hstack for labels.

ValueError: Data cardinality is ambiguous:
  x sizes: 41063
  y sizes: 41429
Please provide data which shares the same first dimension.

This error you are getting is because few of the labels have special characters like - and /. Thus on performing np.hstack(label_tokenizer.texts_to_sequences(train_labels), they are creating additional rows. You can print list of unique train_labels by using print(set(train_labels)).

Here is gist of what I am trying to say -

# These Labels have special character
train_labels = ['Bio-PesticidesandBio-Fertilizers','Old/SenileOrchardRejuvenation']
training_label_seq = np.hstack(label_tokenizer.texts_to_sequences(train_labels))
print("Two labels are converted to Five :",training_label_seq)

# These Labels are fine
train_labels = ['SoilHealthCard', 'PostHarvestPreservation', 'FertilizerUseandAvailability']
training_label_seq = np.hstack(label_tokenizer.texts_to_sequences(train_labels))
print("Three labels are remain three :",training_label_seq)

Output -

Two labels are converted to Five : [17 18 19 51 52]
Three labels are remain three : [20 36  5]

So kindly do the proper preprocessing and eliminate these special characters in train_labels and then use np.hstack(label_tokenizer.texts_to_sequences(train_labels)) on labels. Your model.fit() should work fine after that.

Hope this answers your question. Happy Learning.