python compress and decompress string solution (#309)

* compress string solution

* decompress string solution

* style fix

topics/python/solutions/compress_string_solution.md

@@ -0,0 +1,41 @@
+## Compress String Solution
+
+1. Write a function that gets a string and compresses it
+  - 'aaaabbccc' -> 'a4b2c3'
+  - 'abbbc' -> 'a1b3c1'
+
+```
+def compress_str(mystr: str) -> str:
+
+	result = ''
+
+	if mystr:
+		prevchar = mystr[0]
+	else:
+		return result
+
+	count = 1
+	for nextchar in mystr[1:]:
+		if nextchar == prevchar:
+			count += 1
+		else:
+			result += prevchar + str(count)
+			count = 1
+			prevchar = nextchar
+
+	result += prevchar + str(count)
+	return result
+```
+
+
+2. Write a function that decompresses a given string
+  - 'a4b2c3' -> 'aaaabbccc'
+  - 'a1b3c1' -> 'abbbc'
+
+```
+def decompress_str(mystr: str) -> str:
+	result = ''
+	for index in range(0, len(mystr), 2):
+		result += mystr[index] * int(mystr[index + 1])
+	return result
+```