replace all occurence

replace_all.py

filename_in = "sourcefile.name"
filename_out = "destinationfile.name"

fin = open(filename_in, "r")
fout = open(filename_out, "w")
original_word = "WORD"
replace_by = "DROW"
match_buffer = ""
replace_count = 0

try:
    while True:
        ch = fin.read(1)
        if not ch:
            break
        
        cc = original_word[len(match_buffer)]
        if ch == cc:
            match_buffer = match_buffer + cc
            if len(match_buffer) == len(original_word):
                print("replaced %d" % (replace_count))
                replace_count = replace_count + 1
                match_buffer = ""
                fout.write(replace_by)
        else:
            if len(match_buffer) != 0:
                fout.write(match_buffer)
            fout.write(ch)
            match_buffer = ""
finally:
    fin.close()
    fout.close()

print("total replace: %d" % (replace_count))