how to replace a certain word in a python script code example

Example 1: python replace string in file

#input file
fin = open("data.txt", "rt")
#output file to write the result to
fout = open("out.txt", "wt")
#for each line in the input file
for line in fin:
	#read replace the string and write to output file
	fout.write(line.replace('pyton', 'python'))
#close input and output files
fin.close()
fout.close()

Example 2: python replace text in file

filename = "sample1.txt"
# SAMPLE1.TXT
# Hello World!
# I am a human.

with open(filename, 'r+') as f:
    text = f.read()
    text = re.sub('human', 'cat', text)
    f.seek(0)
    f.write(text)
    f.truncate()

# SAMPLE1.TXT
# Hello World!
# I am a cat.