python 文件操作

writelines() 没换行，不知为何。

f = open('1.txt', 'w')f.write('hello')f.write('world\n')f.writelines ('us')f.writelines ('ddd')f.write('lt')f.close()f = open('1.txt', 'r')str = f.read()print(str)f.seek(0)str = f.tell()print('-------------------------------------')i=0for str in f.readlines():    print('line %d'%(i), str, end='')    i += 1print('\n-------------------------------------')f.seek(0)i=0while 1:    str = f.readline()    if str == '':        break    print('line %d'%(i), str, end='')    i += 1f.close()