Question

所以我有字符串john。我将其打包到一个结构中。打开包装后，如何打印john？当前仅打印j。如果我将字符串更改为Sammy或其他长度不同的名称，是否也一样？我有2个打包和解压缩该结构的函数。我不必担心first_name的长度。该功能可以帮我实现。

结构基本上是

user_id（在本例中为1）
first_name（人的名字。此字符串的长度可以不同。在这种情况下，john）

我的代码

from struct import *

def make_struct(user_id, first_name):
    return pack("is", user_id, first_name)

def deconstruct_struct(structure):
    return unpack("is", structure)

packed = make_struct(1, "john")
unpacked = deconstruct_struct(packed)

print(unpacked[1])

当前输出为：

Answer 1

您需要将字符串的长度添加到格式字符串中：

packed = pack("i4s", 1, "john")
unpacked = unpack("i4s", packed)
print(unpacked[1])
>> john

如果您需要一个可变长度的字符串-> packing and unpacking variable length array/string using the struct module in python

编辑：

您的解决方案可以这样扩展：

from struct import *

def make_struct(user_id, first_name):
    first_name_length = len(first_name)
    fmt = "ii{}s".format(first_name_length) #generate format string with length of first_name
    return pack(fmt, user_id, first_name_length, first_name) #add the length to the pack

def deconstruct_struct(structure):
    user_id, first_name_length = unpack("ii", structure[:8]) #extract only userid and length from the pack
    fmt = "ii{}s".format(first_name_length) #generate the format string like above
    #return unpack(fmt, structure) #this would return a (user_id, length of first name, first_name) tuple
    return (user_id, unpack(fmt, structure)[2]) #this way, we return only the (user_id, first_name) tuple

packed = make_struct(1, "john")
unpacked = deconstruct_struct(packed)

如何从结构中打印字符串？

1 个答案: