# send information to the "Command Output"
print "hello world"

# creat a new file and write it

f = open('helloworld.txt','w')     # creat a txt file in the working directory. w stands for "write". when using w, the program will overwite whatever might have been contained in the file.
f.write('hello world!!')    # write "hello world" to the txt file.
f.close()    # close the file.

f = open('/Users/Yangyang/Documents/acs_230715.dat','w')    # creat a dat file in the given path.
f.write('hello world!!')
f.close()

# read a file

f = open('helloworld.txt','r')    # open the txt file and read from it.
m = f.read()    # copy the contents of the above txt file into m.
print m    # send the information contained in m to the "Command Output"
f.close()

f = open ('/Users/Yangyang/Documents/acs_2_230715.dat','r')    # open the dat file from a special path and read from it.
n = f.read()    # copy the contents of the above dat file into n.
print n
f.close()

# append to a pre-existing file

f = open('helloworld.txt','a')
f.write('n'+'hello world')    # 'n' stands for new line. add 'hello world' in the new line of the txt file.
f.close()