018_IO

#!/usr/bin/env python
# Author:liujun

f = open("test","r",encoding="utf-8")
    # r --> readable
    # r --> writeable
    # r+ --> read and write
    # w+ --> write and read

#print(f.read())

#for i in range(5):
#    print(f.readline())

#for line in f.readlines():
#    print(line.strip())

#for index,line in enumerate(f.readlines()):
#    print(index,line.strip())

#for line in f:  # This kind of traverse is recommanded
#    print(line.strip())

print(f.tell())
print(f.readline())
print(f.tell())
    # Used to get the location of file pointer.
f.seek(10)
    # Used to set the location of file pointer
print(f.read(50))
print(f.readline())
print(f.fileno())
f.flush()
    # Forces the contents of the cache to be written to disk.









How to modify a file

#!/usr/bin/env python
# Author:liujun

f = open("test", "r", encoding="utf-8")
f_new = open("test.bak","w",encoding="utf-8")

for line in f:
    if "iphone" in line:
        line = line.replace("iphone","iphoneX");
    f_new.write(line)
f.close()
f_new.close()