python文件读写操作

代码：

root@linux:/study/python# cat write.py 
#!/usr/bin/python

output_file = open("test.txt","w")
output_file.write("write test\n")
output_file.close()

output_file = open("test.txt","a")
output_file.write("write test\n")
output_file.close()

def sum(input_file, output_file):
	for line in input_file:
		operands = line.split()
		print 'operands', operands
		sum = float(operands[0]) + float(operands[1])
		new_line = line.rstrip() + ' ' + str(sum) + '\n'	
		output_file.write(new_line)
	return

if __name__ == "__main__":
	infile = open("data_in.txt","r")
	outfile = open("data_out.txt","w")
	sum(infile, outfile)
	infile.close()
	outfile.close()

输入文件的内容：

root@linux:/study/python# cat data_in.txt 
111 222
111 333
222 222
222 444

执行过程：

root@linux:/study/python# ./write.py 
operands ['111', '222']
operands ['111', '333']
operands ['222', '222']
operands ['222', '444']
root@linux:/study/python# 

执行后，输出文件的结果：

root@linux:/study/python# cat data_out.txt 
111 222 333.0
111 333 444.0
222 222 444.0
222 444 666.0
root@linux:/study/python#