Grade point average from letter grades.

grades.py

grades_txt = """C+
A-
A-
B+
B-
B
C-
B
B
B
B
A
B+
B+
B
B+
B+
A
C
B
A
B+
C
S
A-
A-
B+
B
A"""

grade_map = {"A":4, "B":3, "C":2, "D":1, "F":0, "S":0}
modifiers = {"+":.25, "-":-0.25}

grades = grades_txt.split("\n")

sum = 0.0
cnt = 0
for g in grades:
	print "Grade: %s" % g
	# Bypass (un)satisfactory
	if g[0] != "S":
		grade_int = float(grade_map[g[0]])
		if len(g) > 1:
			grade_int += modifiers[g[1]]
		sum += grade_int
		cnt += 1
		print "Current grade: %f" % grade_int

print "Total number of grades: %d" % cnt
print "Total sum of grades: %f" % sum
print "Average: %f" % (float(sum) / float(cnt))