Python TensorFlow 字符串：它们是什么以及如何使用它们
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TensorFlow strings: what they are and how to work with them
提问by ckorzhik
When I read file with tf.read_fileI get something with type tf.string. Documentation says only that it is "Variable length byte arrays. Each element of a Tensor is a byte array." (https://www.tensorflow.org/versions/r0.10/resources/dims_types.html). I have no idea how to interpret this.
当我阅读文件时，tf.read_file我得到了 type 的东西tf.string。文档只说它是“可变长度字节数组。张量的每个元素都是一个字节数组。” （https://www.tensorflow.org/versions/r0.10/resources/dims_types.html）。我不知道如何解释这一点。
I can do nothing with this type. In usual python you can get elements by index like my_string[:4], but when I run following code I get an error.
我对这种类型无能为力。在通常的python中，您可以通过索引获取元素，例如my_string[:4]，但是当我运行以下代码时，出现错误。
import tensorflow as tf
import numpy as np
x = tf.constant("This is string")
y = x[:4]
init = tf.initialize_all_variables()
sess = tf.Session()
sess.run(init)
result = sess.run(y)
print result
It says
它说
File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/framework/tensor_shape.py", line 621, in assert_has_rank
raise ValueError("Shape %s must have rank %d" % (self, rank))
ValueError: Shape () must have rank 1
Also I cannot convert my string to tf.float32tensor. It is .flofile and it has magic header "PIEH". This numpy code successfuly convert such header into number (see example here https://stackoverflow.com/a/28016469/4744283) but I can't do that with tensorflow. I tried tf.string_to_number(string, out_type=tf.float32)but it says
我也无法将我的字符串转换为tf.float32张量。它是.flo文件，它有魔术头“PIEH”。此 numpy 代码成功地将此类标头转换为数字（参见此处的示例https://stackoverflow.com/a/28016469/4744283），但我无法使用 tensorflow 做到这一点。我试过了，tf.string_to_number(string, out_type=tf.float32)但它说
tensorflow.python.framework.errors.InvalidArgumentError: StringToNumberOp could not correctly convert string: PIEH
So, what string is? What it's shape is? How can I at least get part of the string? I suppose that if I can get part of it I can just skip "PIEH" part.
那么，什么是字符串？它的形状是什么？我怎样才能至少获得一部分字符串？我想如果我能得到它的一部分，我可以跳过“PIEH”部分。
UPD: I forgot to say that tf.slice(string, [0], [4])also doesn't work with same error.
UPD：我忘了说这tf.slice(string, [0], [4])也不适用于相同的错误。
回答by keveman
Unlike Python, where a string can be treated as a list of characters for the purposes of slicing and such, TensorFlow's tf.strings are indivisible values. For instance, xbelow is a Tensorwith shape (2,)whose each element is a variable length string.
与 Python 不同，在 Python 中，出于切片等目的，可以将字符串视为字符列表，而 TensorFlow 的tf.strings 是不可分割的值。例如，x下面是一个Tensorwith 形状，(2,)其每个元素都是一个可变长度的字符串。
x = tf.constant(["This is a string", "This is another string"])
However, to achieve what you want, TensorFlow provides the tf.decode_rawoperator. It takes a tf.stringtensor as input, but can decode the string into any other primitive data type. For instance, to interpret the string as a tensor of characters, you can do the following :
然而，为了实现你想要的，TensorFlow 提供了tf.decode_raw操作符。它以tf.string张量作为输入，但可以将字符串解码为任何其他原始数据类型。例如，要将字符串解释为字符张量，您可以执行以下操作：
x = tf.constant("This is string")
x = tf.decode_raw(x, tf.uint8)
y = x[:4]
sess = tf.InteractiveSession()
print(y.eval())
# prints [ 84 104 105 115]
