diff --git a/tests/test_zkpytb_logging.py b/tests/test_zkpytb_logging.py
index b47f0a8..558ced1 100644
--- a/tests/test_zkpytb_logging.py
+++ b/tests/test_zkpytb_logging.py
@@ -121,9 +121,9 @@ def test_setup_simple_console_and_file_logger_4(tmpdir):
     """
     logger_name = 'logtest4'
     with LogCapture('zkpytb.logging') as lc2:
-        logger = setup_simple_console_and_file_logger(logger_name, logdir=123)
+        logger = setup_simple_console_and_file_logger(logger_name, logdir=123)  # type: ignore
     err_msg = ('Invalid type for argument "logdir". '
-               'Expected "str", "bytes" or "pathlib.Path". '
+               'Expected "str" or "pathlib.Path". '
                'Received type: {}'.format(type(123)))
     lc2.check(('zkpytb.logging', 'ERROR', err_msg))
     assert len(logger.handlers) == 1
diff --git a/tests/test_zkpytb_pandas.py b/tests/test_zkpytb_pandas.py
index 498608e..0be1239 100644
--- a/tests/test_zkpytb_pandas.py
+++ b/tests/test_zkpytb_pandas.py
@@ -49,7 +49,7 @@ def generate_test_df(df_len, rand_seed):
         'd': np.arange(df_len, dtype=float),
         'e': np.random.RandomState(rand_seed).rand(df_len),
         'f': np.random.RandomState(rand_seed).randn(df_len),
-        'g': np.random.RandomState(rand_seed).random_integers(0, 100, df_len),
+        'g': np.random.RandomState(rand_seed).randint(0, 100 + 1, df_len),
         'n': np.zeros(df_len) + np.nan,
     }, index=range(df_len))
 
@@ -116,11 +116,13 @@ def test_move_col_to_beginning_of_df(df1):
 
 def test_compare_df_cols_mode1(df1, df2):
     res = compare_df_cols([df1, df2], ['e', 'f', 'g'], mode=1)
+    assert res is not None
     assert list(res.columns) == ['e_1', 'e_2', 'f_1', 'f_2', 'g_1', 'g_2']
 
 
 def test_compare_df_cols_mode2(df1, df2):
     res = compare_df_cols([df1, df2], ['e', 'f', 'g'], mode=2)
+    assert res is not None
     assert list(res.columns) == ['e_1', 'f_1', 'g_1', 'e_2', 'f_2', 'g_2']
 
 
diff --git a/tests/test_zkpytb_utils.py b/tests/test_zkpytb_utils.py
index c5eda10..f50dec8 100644
--- a/tests/test_zkpytb_utils.py
+++ b/tests/test_zkpytb_utils.py
@@ -6,6 +6,7 @@
 import os
 import pytest
 import subprocess
+from pathlib import Path
 
 
 from zkpytb.utils import (
@@ -24,29 +25,36 @@ def a_hash_method(request):
 def test_hashstring_hashmethods(a_hash_method):
     hash_res1 = hashstring(b'', hash_method=a_hash_method)
     hash_res2 = hashstring(b'test', hash_method=a_hash_method)
-    assert isinstance(hash_res1, str)
-    assert len(hash_res1) > 0
+    hash_res3 = hashstring(b'test', hash_method=a_hash_method)
+    assert all(isinstance(res, str) for res in [hash_res1, hash_res2, hash_res3])
+    assert all(len(res) > 0 for res in [hash_res1, hash_res2, hash_res3])
     assert hash_res1 != hash_res2
+    assert hash_res2 == hash_res3
 
 
-def test_hashfile_hashmethods(a_hash_method, tmpdir):
-    f1 = tmpdir.join("hashfile1.txt")
-    f2 = tmpdir.join("hashfile2.txt")
-    f1.write("content1")
-    f2.write("content2")
+def test_hashfile_hashmethods(a_hash_method, tmp_path: Path):
+    f1 = tmp_path / "hashfile1.txt"
+    f2 = tmp_path / "hashfile2.txt"
+    f3 = tmp_path / "hashfile3.txt"
+    f1.write_text("content1")
+    f2.write_text("content2")
+    f3.write_text("content2")
     hashfile_res1 = hashfile(f1, hash_method=a_hash_method)
     hashfile_res2 = hashfile(f2, hash_method=a_hash_method)
-    assert isinstance(hashfile_res1, str)
-    assert len(hashfile_res1) > 0
+    hashfile_res3 = hashfile(f3, hash_method=a_hash_method)
+    assert all(isinstance(res, str) for res in [hashfile_res1, hashfile_res2, hashfile_res3])
+    assert all(len(res) > 0 for res in [hashfile_res1, hashfile_res2, hashfile_res3])
     assert hashfile_res1 != hashfile_res2
+    assert hashfile_res2 == hashfile_res3
 
 
 @pytest.mark.xfail(reason="Tox temp dir is located under the main git repository of the project...")
-def test_get_git_hash_nogit(tmpdir):
-    curdir = os.getcwd()
+def test_get_git_hash_nogit(tmp_path: Path):
+    curdir = Path.cwd()
     try:
-        nogit_dir = tmpdir.mkdir("nogit_dir")
-        os.chdir(str(nogit_dir))
+        nogit_dir = (tmp_path / "nogit_dir").mkdir()
+        assert nogit_dir is not None
+        os.chdir(nogit_dir)
         git_hash = get_git_hash()
     finally:
         os.chdir(curdir)
@@ -54,11 +62,12 @@ def test_get_git_hash_nogit(tmpdir):
     assert git_hash == ''
 
 
-def test_get_git_hash_emptygit(tmpdir):
-    curdir = os.getcwd()
+def test_get_git_hash_emptygit(tmp_path: Path):
+    curdir = Path.cwd()
     try:
-        emptygit_dir = tmpdir.mkdir("emptygit_dir")
-        os.chdir(str(emptygit_dir))
+        emptygit_dir: Path = tmp_path / "emptygit_dir"
+        emptygit_dir.mkdir()
+        os.chdir(emptygit_dir)
         subprocess.check_call(['git', 'init'])
         git_hash = get_git_hash()
     finally:
@@ -67,11 +76,12 @@ def test_get_git_hash_emptygit(tmpdir):
     assert git_hash == ''
 
 
-def test_get_git_hash_minimalgit(tmpdir):
-    curdir = os.getcwd()
+def test_get_git_hash_minimalgit(tmp_path: Path):
+    curdir = Path.cwd()
     try:
-        minimalgit_dir = tmpdir.mkdir("minimalgit_dir")
-        minimalgit_dir.join('testfile.txt').write('minimalgit')
+        minimalgit_dir: Path = tmp_path / "minimalgit_dir"
+        minimalgit_dir.mkdir()
+        (minimalgit_dir / 'testfile.txt').write_text('minimalgit')
         os.chdir(str(minimalgit_dir))
         subprocess.check_call(['git', 'init'])
         subprocess.check_call(['git', 'config', 'user.email', 'test@domain.invalid'])
diff --git a/zkpytb/dicts.py b/zkpytb/dicts.py
index eac442f..b8a625c 100644
--- a/zkpytb/dicts.py
+++ b/zkpytb/dicts.py
@@ -9,6 +9,7 @@
 import json
 
 from collections import OrderedDict
+from typing import Any, Callable, Dict, Iterator, List
 
 from zkpytb.json import JSONEncoder
 
@@ -43,18 +44,18 @@ class AutoOrderedDict(OrderedDict, AutoDict):
     _base_class = OrderedDict
 
 
-def filter_dict_callfunc(dict_in, func):
+def filter_dict_callfunc(dict_in: Dict, func: Callable[..., bool]) -> Dict:
     assert isinstance(dict_in, dict)
     assert callable(func)
     return {k: v for (k, v) in dict_in.items() if func(k, v)}
 
 
-def filter_dict_only_scalar_values(dict_in):
+def filter_dict_only_scalar_values(dict_in: Dict) -> Dict:
     assert isinstance(dict_in, dict)
     return {k: v for (k, v) in dict_in.items() if not hasattr(v, '__iter__')}
 
 
-def filter_dict_with_keylist(dict_in, keylist, blacklistmode=False):
+def filter_dict_with_keylist(dict_in: Dict, keylist: List, blacklistmode=False) -> Dict:
     assert isinstance(dict_in, dict)
     assert isinstance(keylist, list)
     if blacklistmode:
@@ -63,7 +64,7 @@ def filter_dict_with_keylist(dict_in, keylist, blacklistmode=False):
         return {k: v for (k, v) in dict_in.items() if k in keylist}
 
 
-def mergedicts(dict1, dict2):
+def mergedicts(dict1, dict2) -> Iterator[Any]:
     assert isinstance(dict1, dict)
     assert isinstance(dict2, dict)
     for k in set(dict1.keys()).union(dict2.keys()):
@@ -81,11 +82,11 @@ def mergedicts(dict1, dict2):
             yield (k, dict2[k])
 
 
-def dict_stable_json_repr(dict_in):
+def dict_stable_json_repr(dict_in: Dict) -> str:
     return json.dumps(dict_in, sort_keys=True, cls=JSONEncoder)
 
 
-def hashdict(dict_in, method='sha1'):
+def hashdict(dict_in: Dict, method='sha1') -> str:
     assert isinstance(dict_in, dict)
     h = hashlib.new(method)
     dict_repr = dict_stable_json_repr(dict_in)
@@ -93,7 +94,7 @@ def hashdict(dict_in, method='sha1'):
     return h.hexdigest()
 
 
-def dict_values_map(f, d):
+def dict_values_map(f: Callable, d: Dict) -> Dict:
     """
     Simple helper to apply a function to the values of a dictionary.
 
diff --git a/zkpytb/json.py b/zkpytb/json.py
index b29e142..cca095f 100644
--- a/zkpytb/json.py
+++ b/zkpytb/json.py
@@ -16,6 +16,7 @@ class JSONEncoder(json.JSONEncoder):
     """
     A custom JSONEncoder that can handle a bit more data types than the one from stdlib.
     """
+
     def default(self, o):
         # early passthrough if it works by default
         try:
diff --git a/zkpytb/logging.py b/zkpytb/logging.py
index 16b9258..241f04d 100644
--- a/zkpytb/logging.py
+++ b/zkpytb/logging.py
@@ -1,14 +1,18 @@
 import logging
 import logging.config
 from pathlib import Path
+from typing import Mapping, Optional, Union
 
 
 mylogger = logging.getLogger('zkpytb.logging')
 
 
-def setup_simple_console_and_file_logger(logger_name, logfile=True,
-                                         logdir=None, logfilename=None,
-                                         log_level='DEBUG', options=None):
+def setup_simple_console_and_file_logger(logger_name: str,
+                                         logfile=True,
+                                         logdir: Optional[Union[str, Path]] = None,
+                                         logfilename: Optional[Union[str, Path]] = None,
+                                         log_level: str = 'DEBUG',
+                                         options: Optional[Mapping[str, str]] = None) -> logging.Logger:
     """
     TODOC
     """
@@ -26,7 +30,7 @@ def setup_simple_console_and_file_logger(logger_name, logfile=True,
             log_directory = Path(logdir)
         except TypeError:
             mylogger.exception('Invalid type for argument "logdir". '
-                               'Expected "str", "bytes" or "pathlib.Path". '
+                               'Expected "str" or "pathlib.Path". '
                                'Received type: {}'.format(type(logdir)))
             do_file_logging = False
         else:
diff --git a/zkpytb/pandas.py b/zkpytb/pandas.py
index d9bcd0e..d724adf 100644
--- a/zkpytb/pandas.py
+++ b/zkpytb/pandas.py
@@ -4,6 +4,8 @@
 Author: Marc Gallet (2017)
 """
 
+from typing import List, Optional, Tuple
+
 try:
     import numpy as np
     import pandas as pd
@@ -17,10 +19,12 @@
 
 
 # More percentiles when using pd.describe()
-extended_percentiles = [.01, .05, .25, .5, .75, .95, .99]
+extended_percentiles: List[float] = [.01, .05, .25, .5, .75, .95, .99]
 
 
-def tdescr(df_in, percentiles=None, disp=True):
+def tdescr(df_in: pd.DataFrame,
+           percentiles: Optional[List[float]] = None,
+           disp: bool = True) -> pd.DataFrame:
     """
     Helper function to display and return the transposition
     of the output of DataFrame.describe(). This means that
@@ -48,7 +52,7 @@ def tdescr(df_in, percentiles=None, disp=True):
     return tdescr_out
 
 
-def df_query_with_ratio(df_in, query, ratio_name='ratio'):
+def df_query_with_ratio(df_in: pd.DataFrame, query: str, ratio_name='ratio') -> Tuple[pd.DataFrame, float]:
     """
     This function calls the .query() method on a DataFrame
     and additionally computes the ratio of resulting rows
@@ -63,7 +67,7 @@ def df_query_with_ratio(df_in, query, ratio_name='ratio'):
     return df_out, ratio
 
 
-def remove_outliers(df_in, column, sigma=3):
+def remove_outliers(df_in: pd.DataFrame, column, sigma: float = 3) -> pd.DataFrame:
     """
     Very simple filter that removes outlier rows
     from a DataFrame based on the distance from the
@@ -72,7 +76,7 @@ def remove_outliers(df_in, column, sigma=3):
     return df_in[np.abs(df_in[column] - df_in[column].mean()) <= (sigma * df_in[column].std())]
 
 
-def only_outliers(df_in, column, sigma=3):
+def only_outliers(df_in: pd.DataFrame, column, sigma: float = 3) -> pd.DataFrame:
     """
     Very simple filter that only keeps outlier rows
     from a DataFrame based on the distance from the
@@ -81,7 +85,7 @@ def only_outliers(df_in, column, sigma=3):
     return df_in[np.abs(df_in[column] - df_in[column].mean()) > (sigma * df_in[column].std())]
 
 
-def move_col_to_beginning_of_df(df_in, colname):
+def move_col_to_beginning_of_df(df_in: pd.DataFrame, colname: str) -> pd.DataFrame:
     """
     Small helper to move a column to the beginning of the DataFrame
     """
@@ -90,7 +94,7 @@ def move_col_to_beginning_of_df(df_in, colname):
     return df_in.reindex(columns=cols)
 
 
-def compare_df_cols(df_list, col_list, mode=1):
+def compare_df_cols(df_list: List[pd.DataFrame], col_list: List[str], mode=1) -> Optional[pd.DataFrame]:
     """
     Helper to compare the values of common columns between different dataframes
 
@@ -98,11 +102,11 @@ def compare_df_cols(df_list, col_list, mode=1):
     Mode 2: iterate over DataFrames as top level and columns as second level
     """
     if mode == 1:
-        colstoconcat = [df.loc[:, col].rename(df.loc[:, col].name + '_' + str(i + 1))
+        colstoconcat = [df.loc[:, col].rename(str(df.loc[:, col].name) + '_' + str(i + 1))
                         for col in col_list
                         for i, df in enumerate(df_list)]
     elif mode == 2:
-        colstoconcat = [df.loc[:, col].rename(df.loc[:, col].name + '_' + str(i + 1))
+        colstoconcat = [df.loc[:, col].rename(str(df.loc[:, col].name) + '_' + str(i + 1))
                         for i, df in enumerate(df_list)
                         for col in col_list]
     else:
@@ -140,7 +144,7 @@ def _percentile(x):
     return _percentile
 
 
-def describe_numeric_1d(series):
+def describe_numeric_1d(series: pd.Series):
     """
     Patched version of pandas' .describe() function for Series
     which includes the calculation of the median absolute deviation and interquartile range
@@ -149,7 +153,7 @@ def describe_numeric_1d(series):
     and all other stats are set to np.nan
     """
     stat_index = (['count', 'mean', 'std', 'mad', 'mad_c1', 'iqr', 'min']
-                  + pd.io.formats.format.format_percentiles(extended_percentiles) + ['max'])
+                  + pd.io.formats.format.format_percentiles(extended_percentiles) + ['max'])  # type: ignore
     if series.empty:
         # [0, np.nan, np.nan, ..., np.nan]
         d = [0] + [np.nan] * (len(stat_index) - 1)
diff --git a/zkpytb/priorityqueue.py b/zkpytb/priorityqueue.py
index 2fe71c8..97bd3c3 100644
--- a/zkpytb/priorityqueue.py
+++ b/zkpytb/priorityqueue.py
@@ -16,12 +16,13 @@ class EmptyQueueError(Exception):
 
 class PriorityQueue:
     """Based on https://docs.python.org/3/library/heapq.html#priority-queue-implementation-notes"""
+
     def __init__(self, name=''):
         self.name = name
         self.pq = []                         # list of entries arranged in a heap
         self.entry_finder = {}               # mapping of tasks to entries
         self.counter = itertools.count()     # unique sequence count
-        self.num_tasks = 0                  # track the number of tasks in the queue
+        self.num_tasks = 0                   # track the number of tasks in the queue
 
     def __len__(self):
         return self.num_tasks
diff --git a/zkpytb/utils.py b/zkpytb/utils.py
index dc00680..5492daa 100644
--- a/zkpytb/utils.py
+++ b/zkpytb/utils.py
@@ -9,11 +9,13 @@
 import logging
 import subprocess
 
+from pathlib import Path
+from typing import Union
 
 mylogger = logging.getLogger('zkpytb.utils')
 
 
-def hashfile(filepath, hash_method='sha256', BLOCKSIZE=65536):
+def hashfile(filepath: Union[str, Path], hash_method: str = 'sha256', BLOCKSIZE: int = 65536) -> str:
     """Hash a file"""
 
     hasher = hashlib.new(hash_method)
@@ -27,15 +29,15 @@ def hashfile(filepath, hash_method='sha256', BLOCKSIZE=65536):
     return hasher.hexdigest()
 
 
-def hashstring(inputstring, hash_method='sha256'):
-    """Hash a file"""
+def hashstring(inputstring: bytes, hash_method: str = 'sha256') -> str:
+    """Hash a string"""
 
     hasher = hashlib.new(hash_method)
     hasher.update(inputstring)
     return hasher.hexdigest()
 
 
-def get_git_hash(rev='HEAD'):
+def get_git_hash(rev: str = 'HEAD') -> str:
     """Get the git hash of the current directory"""
 
     git_hash = ''