from struct import Struct
def write_records(records, format, f):
'''
Write a sequence of tuples to a binary file of structures.
'''
record_struct = Struct(format)
for r in records:
f.write(record_struct.pack(*r))
if name == ' main ':
records = [ (1, 2.3, 4.5),
(6, 7.8, 9.0),
(12, 13.4, 56.7) ]
with open('data.b', 'wb') as f:
write_records(records, '<idd', f)
from struct import Struct
def read_records(format, f):
record_struct = Struct(format)
chunks = iter(lambda: f.read(record_struct.size), b'')
return (record_struct.unpack(chunk) for chunk in chunks)
if name == ' main ':
with open('data.b','rb') as f:
for rec in read_records('<idd', f):
# Process rec
...
用"*"和\xNN. 例子:写入1024个二进制值0x00:
file('a.bin','wb').write('\x00'*1024)
在文件尾再添加1024个0x01 :
file('a.bin','ab').write('\x01'*1024)
精确 是什么意思？ 指定具体要写入的数字1024还不够精确？
如果要保证数据实际写入，刷新IO缓冲区，调用fush或close方法
这有什么难的吗？你把你的二进制数据可以转成文本串插入，就跟普通的插入一样啊。
import MySQLdb, cPickle
# Connect to a DB, e.g., the test DB on your localhost, and get a cursor
connection = MySQLdb.connect(db="test")
cursor = connection.cursor( )
# Make a new table for experimentation
cursor.execute("CREATE TABLE justatest (name TEXT, ablob BLOB)")
try:
# Prepare some BLOBs to insert in the table
names = 'aramis', 'athos', 'porthos'
data = { }
for name in names:
datum = list(name)
datum.sort( )
data[name] = cPickle.dumps(datum, 2)
# Perform the insertions
sql = "INSERT INTO justatest VALUES(%s, %s)"
for name in names:
cursor.execute(sql, (name, MySQLdb.escape_string(data[name])) )
# Recover the data so you can check back
sql = "SELECT name, ablob FROM justatest ORDER BY name"
cursor.execute(sql)
for name, blob in cursor.fetchall( ):
print name, cPickle.loads(blob), cPickle.loads(data[name])
finally:
# Done. Remove the table and close the connection.
cursor.execute("DROP TABLE justatest")
connection.close( )
