diff --git a/TTS/bin/train_wavernn_vocoder.py b/TTS/bin/train_wavernn_vocoder.py
index 533fe0ce..78984510 100644
--- a/TTS/bin/train_wavernn_vocoder.py
+++ b/TTS/bin/train_wavernn_vocoder.py
@@ -1,8 +1,5 @@
 import argparse
-import math
 import os
-import pickle
-import shutil
 import sys
 import traceback
 import time
@@ -11,7 +8,8 @@ import random
 
 import torch
 from torch.utils.data import DataLoader
-from torch.utils.data.distributed import DistributedSampler
+
+# from torch.utils.data.distributed import DistributedSampler
 
 from TTS.tts.utils.visual import plot_spectrogram
 from TTS.utils.audio import AudioProcessor
@@ -30,7 +28,6 @@ from TTS.utils.generic_utils import (
 )
 from TTS.vocoder.datasets.wavernn_dataset import WaveRNNDataset
 from TTS.vocoder.datasets.preprocess import (
-    load_wav_data,
     find_feat_files,
     load_wav_feat_data,
     preprocess_wav_files,
@@ -322,7 +319,7 @@ def main(args):  # pylint: disable=redefined-outer-name
                 CONFIG.data_path, mel_feat_path, CONFIG.eval_split_size
             )
         else:
-            print(f" > No feature data found. Preprocessing...")
+            print(" > No feature data found. Preprocessing...")
             # preprocessing feature data from given wav files
             preprocess_wav_files(OUT_PATH, CONFIG, ap)
             eval_data, train_data = load_wav_feat_data(
diff --git a/TTS/vocoder/datasets/wavernn_dataset.py b/TTS/vocoder/datasets/wavernn_dataset.py
index 1b0a8077..5d5b9f15 100644
--- a/TTS/vocoder/datasets/wavernn_dataset.py
+++ b/TTS/vocoder/datasets/wavernn_dataset.py
@@ -1,5 +1,3 @@
-import os
-import glob
 import torch
 import numpy as np
 from torch.utils.data import Dataset
@@ -42,7 +40,7 @@ class WaveRNNDataset(Dataset):
         wavpath, feat_path = self.item_list[index]
         m = np.load(feat_path.replace("/quant/", "/mel/"))
         # x = self.wav_cache[index]
-        if 5 > m.shape[-1]:
+        if m.shape[-1] < 5:
             print(" [!] Instance is too short! : {}".format(wavpath))
             self.item_list[index] = self.item_list[index + 1]
             feat_path = self.item_list[index]
diff --git a/TTS/vocoder/models/wavernn.py b/TTS/vocoder/models/wavernn.py
index e1c4365f..9b637a6a 100644
--- a/TTS/vocoder/models/wavernn.py
+++ b/TTS/vocoder/models/wavernn.py
@@ -42,7 +42,7 @@ class MelResNet(nn.Module):
         self.conv_in = nn.Conv1d(in_dims, compute_dims, kernel_size=k_size, bias=False)
         self.batch_norm = nn.BatchNorm1d(compute_dims)
         self.layers = nn.ModuleList()
-        for i in range(res_blocks):
+        for _ in range(res_blocks):
             self.layers.append(ResBlock(compute_dims))
         self.conv_out = nn.Conv1d(compute_dims, res_out_dims, kernel_size=1)
 
@@ -365,7 +365,8 @@ class WaveRNN(nn.Module):
             (i * b_size, seq_len * b_size, b_size, gen_rate, realtime_ratio),
         )
 
-    def get_gru_cell(self, gru):
+    @staticmethod
+    def get_gru_cell(gru):
         gru_cell = nn.GRUCell(gru.input_size, gru.hidden_size)
         gru_cell.weight_hh.data = gru.weight_hh_l0.data
         gru_cell.weight_ih.data = gru.weight_ih_l0.data
@@ -373,13 +374,14 @@ class WaveRNN(nn.Module):
         gru_cell.bias_ih.data = gru.bias_ih_l0.data
         return gru_cell
 
-    def pad_tensor(self, x, pad, side="both"):
+    @staticmethod
+    def pad_tensor(x, pad, side="both"):
         # NB - this is just a quick method i need right now
         # i.e., it won't generalise to other shapes/dims
         b, t, c = x.size()
         total = t + 2 * pad if side == "both" else t + pad
         padded = torch.zeros(b, total, c).cuda()
-        if side == "before" or side == "both":
+        if side in ("before", "both"):
             padded[:, pad : pad + t, :] = x
         elif side == "after":
             padded[:, :t, :] = x
diff --git a/TTS/vocoder/utils/distribution.py b/TTS/vocoder/utils/distribution.py
index bfcbdd3f..705c14dc 100644
--- a/TTS/vocoder/utils/distribution.py
+++ b/TTS/vocoder/utils/distribution.py
@@ -11,7 +11,11 @@ def gaussian_loss(y_hat, y, log_std_min=-7.0):
     mean = y_hat[:, :, :1]
     log_std = torch.clamp(y_hat[:, :, 1:], min=log_std_min)
     # TODO: replace with pytorch dist
-    log_probs = -0.5 * (- math.log(2.0 * math.pi) - 2. * log_std - torch.pow(y - mean, 2) * torch.exp((-2.0 * log_std)))
+    log_probs = -0.5 * (
+        -math.log(2.0 * math.pi)
+        - 2.0 * log_std
+        - torch.pow(y - mean, 2) * torch.exp((-2.0 * log_std))
+    )
     return log_probs.squeeze().mean()
 
 
@@ -19,7 +23,10 @@ def sample_from_gaussian(y_hat, log_std_min=-7.0, scale_factor=1.0):
     assert y_hat.size(2) == 2
     mean = y_hat[:, :, :1]
     log_std = torch.clamp(y_hat[:, :, 1:], min=log_std_min)
-    dist = Normal(mean, torch.exp(log_std), )
+    dist = Normal(
+        mean,
+        torch.exp(log_std),
+    )
     sample = dist.sample()
     sample = torch.clamp(torch.clamp(sample, min=-scale_factor), max=scale_factor)
     del dist
@@ -36,11 +43,12 @@ def log_sum_exp(x):
 
 
 # It is adapted from https://github.com/r9y9/wavenet_vocoder/blob/master/wavenet_vocoder/mixture.py
-def discretized_mix_logistic_loss(y_hat, y, num_classes=65536,
-                                  log_scale_min=None, reduce=True):
+def discretized_mix_logistic_loss(
+    y_hat, y, num_classes=65536, log_scale_min=None, reduce=True
+):
     if log_scale_min is None:
         log_scale_min = float(np.log(1e-14))
-    y_hat = y_hat.permute(0,2,1)
+    y_hat = y_hat.permute(0, 2, 1)
     assert y_hat.dim() == 3
     assert y_hat.size(1) % 3 == 0
     nr_mix = y_hat.size(1) // 3
@@ -50,17 +58,17 @@ def discretized_mix_logistic_loss(y_hat, y, num_classes=65536,
 
     # unpack parameters. (B, T, num_mixtures) x 3
     logit_probs = y_hat[:, :, :nr_mix]
-    means = y_hat[:, :, nr_mix:2 * nr_mix]
-    log_scales = torch.clamp(y_hat[:, :, 2 * nr_mix:3 * nr_mix], min=log_scale_min)
+    means = y_hat[:, :, nr_mix : 2 * nr_mix]
+    log_scales = torch.clamp(y_hat[:, :, 2 * nr_mix : 3 * nr_mix], min=log_scale_min)
 
     # B x T x 1 -> B x T x num_mixtures
     y = y.expand_as(means)
 
     centered_y = y - means
     inv_stdv = torch.exp(-log_scales)
-    plus_in = inv_stdv * (centered_y + 1. / (num_classes - 1))
+    plus_in = inv_stdv * (centered_y + 1.0 / (num_classes - 1))
     cdf_plus = torch.sigmoid(plus_in)
-    min_in = inv_stdv * (centered_y - 1. / (num_classes - 1))
+    min_in = inv_stdv * (centered_y - 1.0 / (num_classes - 1))
     cdf_min = torch.sigmoid(min_in)
 
     # log probability for edge case of 0 (before scaling)
@@ -77,34 +85,35 @@ def discretized_mix_logistic_loss(y_hat, y, num_classes=65536,
     mid_in = inv_stdv * centered_y
     # log probability in the center of the bin, to be used in extreme cases
     # (not actually used in our code)
-    log_pdf_mid = mid_in - log_scales - 2. * F.softplus(mid_in)
+    log_pdf_mid = mid_in - log_scales - 2.0 * F.softplus(mid_in)
 
     # tf equivalent
-    """
-    log_probs = tf.where(x < -0.999, log_cdf_plus,
-                         tf.where(x > 0.999, log_one_minus_cdf_min,
-                                  tf.where(cdf_delta > 1e-5,
-                                           tf.log(tf.maximum(cdf_delta, 1e-12)),
-                                           log_pdf_mid - np.log(127.5))))
-    """
+
+    # log_probs = tf.where(x < -0.999, log_cdf_plus,
+    #                      tf.where(x > 0.999, log_one_minus_cdf_min,
+    #                               tf.where(cdf_delta > 1e-5,
+    #                                        tf.log(tf.maximum(cdf_delta, 1e-12)),
+    #                                        log_pdf_mid - np.log(127.5))))
+
     # TODO: cdf_delta <= 1e-5 actually can happen. How can we choose the value
     # for num_classes=65536 case? 1e-7? not sure..
     inner_inner_cond = (cdf_delta > 1e-5).float()
 
-    inner_inner_out = inner_inner_cond * \
-        torch.log(torch.clamp(cdf_delta, min=1e-12)) + \
-        (1. - inner_inner_cond) * (log_pdf_mid - np.log((num_classes - 1) / 2))
+    inner_inner_out = inner_inner_cond * torch.log(
+        torch.clamp(cdf_delta, min=1e-12)
+    ) + (1.0 - inner_inner_cond) * (log_pdf_mid - np.log((num_classes - 1) / 2))
     inner_cond = (y > 0.999).float()
-    inner_out = inner_cond * log_one_minus_cdf_min + (1. - inner_cond) * inner_inner_out
+    inner_out = (
+        inner_cond * log_one_minus_cdf_min + (1.0 - inner_cond) * inner_inner_out
+    )
     cond = (y < -0.999).float()
-    log_probs = cond * log_cdf_plus + (1. - cond) * inner_out
+    log_probs = cond * log_cdf_plus + (1.0 - cond) * inner_out
 
     log_probs = log_probs + F.log_softmax(logit_probs, -1)
 
     if reduce:
         return -torch.mean(log_sum_exp(log_probs))
-    else:
-        return -log_sum_exp(log_probs).unsqueeze(-1)
+    return -log_sum_exp(log_probs).unsqueeze(-1)
 
 
 def sample_from_discretized_mix_logistic(y, log_scale_min=None):
@@ -127,26 +136,27 @@ def sample_from_discretized_mix_logistic(y, log_scale_min=None):
 
     # sample mixture indicator from softmax
     temp = logit_probs.data.new(logit_probs.size()).uniform_(1e-5, 1.0 - 1e-5)
-    temp = logit_probs.data - torch.log(- torch.log(temp))
+    temp = logit_probs.data - torch.log(-torch.log(temp))
     _, argmax = temp.max(dim=-1)
 
     # (B, T) -> (B, T, nr_mix)
     one_hot = to_one_hot(argmax, nr_mix)
     # select logistic parameters
-    means = torch.sum(y[:, :, nr_mix:2 * nr_mix] * one_hot, dim=-1)
-    log_scales = torch.clamp(torch.sum(
-        y[:, :, 2 * nr_mix:3 * nr_mix] * one_hot, dim=-1), min=log_scale_min)
+    means = torch.sum(y[:, :, nr_mix : 2 * nr_mix] * one_hot, dim=-1)
+    log_scales = torch.clamp(
+        torch.sum(y[:, :, 2 * nr_mix : 3 * nr_mix] * one_hot, dim=-1), min=log_scale_min
+    )
     # sample from logistic & clip to interval
     # we don't actually round to the nearest 8bit value when sampling
     u = means.data.new(means.size()).uniform_(1e-5, 1.0 - 1e-5)
-    x = means + torch.exp(log_scales) * (torch.log(u) - torch.log(1. - u))
+    x = means + torch.exp(log_scales) * (torch.log(u) - torch.log(1.0 - u))
 
-    x = torch.clamp(torch.clamp(x, min=-1.), max=1.)
+    x = torch.clamp(torch.clamp(x, min=-1.0), max=1.0)
 
     return x
 
 
-def to_one_hot(tensor, n, fill_with=1.):
+def to_one_hot(tensor, n, fill_with=1.0):
     # we perform one hot encore with respect to the last axis
     one_hot = torch.FloatTensor(tensor.size() + (n,)).zero_()
     if tensor.is_cuda: