diff --git a/maths/average_welford.py b/maths/average_welford.py
new file mode 100644
index 000000000000..522a34adfc06
--- /dev/null
+++ b/maths/average_welford.py
@@ -0,0 +1,21 @@
+def average_welford(values: list) -> float:
+    """
+      >>> average_welford([1, 2, 3, 4, 5])
+      3.0
+      >>> average_welford([1.2329435, 2.209462409, 3.230925, 4.47626462, 5.2938759204])
+      3.2886942898799996
+      >>> average_welford([-57386462.2329435, 2246262.209462409, 4632463.230925, 856737354.47626462, -243664265.2938759204])
+      112513070.4779665
+    """
+    avg = 0.0
+    """while looping through the list,
+       we calculate the average of the
+       current element and the average
+       of the elements before it"""
+    for index in range(0, len(values)):
+      avg += (values[index]-avg)/(index+1)
+    return avg
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
\ No newline at end of file
diff --git a/strings/censor.py b/strings/censor.py
new file mode 100644
index 000000000000..935283f5c8ef
--- /dev/null
+++ b/strings/censor.py
@@ -0,0 +1,26 @@
+def censor(txt: str, word: str) -> str:
+    """
+    >>> censor("one two three", "one")
+    *** two three
+    >>> censor("email, password", "password")
+    email, ********
+    >>> censor("pin: 2536", "2536")
+    pin: ****
+
+    """
+
+    txt_lst = txt.split()
+    #here we loop through a list which consists of words from the text we should censor
+    for index, word1 in enumerate(txt_lst):
+      if word1 == word:
+        txt_lst[index] = "*" * len(word1)
+    txt = ""
+    #here we combine all of the split words in txt_lst into one string
+    for word1 in txt_lst:
+      txt += word1 + " "
+    txt = txt[:-1]
+    return txt
+    
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
\ No newline at end of file
diff --git a/strings/decrypt.py b/strings/decrypt.py
new file mode 100644
index 000000000000..b5fcd1b83122
--- /dev/null
+++ b/strings/decrypt.py
@@ -0,0 +1,38 @@
+def decrypt(txt: str, symbol: str) -> str:
+    """
+    >>> decrypt("o$ne", "$")
+    one
+    >>> decrypt("dec@rypt", "@")
+    decrypt
+    >>> decrypt("p#ython cod#e", "#")
+    python code
+
+    """
+    #here we split the string we need to decypher into a list
+    txt_lst = txt.split()
+    res_str = ""
+    #we create a for loop which loops through the newly created list
+    for word1 in txt_lst:
+      #here we convert the current word we got through the loop into a list of charachters
+      word1_lst = list(word1)
+      #we loop through each charachter in the newly created list of charachters form the word we are looping throuh
+      for char1 in word1_lst:
+        #we set a condition, where if the symbol the loop is currently on corresponds to the symbol we need to remove, we stop on it and examine it
+        if char1 == symbol:
+          #we find the charachters index from the word
+          indx = word1.index(char1)
+          #we remove the list (the list which contains every element and characahter from the word we are looping throuh) element with the same index from the list.
+          word1_lst[indx] = ""
+      res_wrd = ""
+      #we loop throuh the list containing all the charachters from the word, and append those charachters to a new string
+      for char1 in word1_lst:
+        res_wrd += char1
+      #here we add the newly created, decyphered word to a new string which will contain our full result
+      res_str += res_wrd + " "
+    res_str = res_str[:-1]
+    #and here we return out the final result
+    return res_str
+
+if __name__ == "__main__":
+  import doctest
+  doctest.testmod()
\ No newline at end of file