What is StringIO in python used for in reality?

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I am not a pro and I have been scratching my head over understanding what exactly StringIO is used for. I have been looking around the internet for some examples. However, almost all of the examples are very abstract. And they just show "how" to use it. But none of them show "why" and "in which circumstances" one should/will use it? Thanks in advance

p.s. not to be confused with this question on stackoverflow: StringIO Usage which compares string and StringIo.

It's used when you have some API that only takes files, but you need to use a string. For example, to compress a string using the gzip module in Python 2:

import gzip
import StringIO

stringio = StringIO.StringIO()
gzip_file = gzip.GzipFile(fileobj=stringio, mode='w')
gzip_file.write('Hello World')
gzip_file.close()

stringio.getvalue()

The StringIO module, -example-1.py That man is depriving a village somewhere of a computer scientist. StringIO ([buffer]) ¶ When a StringIO object is created, it can be initialized to an existing string by passing the string to the constructor. If no string is given, the StringIO will start empty. In both cases, the initial file position starts at zero. The StringIO object can accept either Unicode or 8-bit strings, but mixing the two may take some care.

StringIO gives you file-like access to strings, so you can use an existing module that deals with a file and change almost nothing and make it work with strings.

For example, say you have a logger that writes things to a file and you want to instead send the log output over the network. You can read the file and write its contents to the network, or you can write the log to a StringIO object and ship it off to its network destination without touching the filesystem. StringIO makes it easy to do it the first way then switch to the second way.

7.5. StringIO — Read and write strings as files, object can accept either Unicode or 8-bit strings, but mixing the two may take some care. This Python example uses the StringIO class from the io namespace. StringIO writes to strings like files. StringIO writes to strings. It uses a syntax similar to that for files. We can use print method calls, or invoke the write method. StringIO has performance advantages for creating large strings.

In cases where you want a file-like object that ACTS like a file, but is writing to an in-memory string buffer: StringIO is the tool. If you're building large strings, such as plain-text documents, and doing a lot of string concatenation, you might find it easier to just use StringIO instead of a bunch of mystr += 'more stuff\n' type of operations.

Python StringIO And BytesIO Example ·, are methods that manipulate string and bytes data in memory, this make memory data manipulation use the consistent API as read and write files. When you use `print()` in python the output goes to standard output or `sys.stdout`. You can directly call `sys.stdout.write()` instead of using `print()`, but you can also completely replace `sys.stdout` with another stream. This example will show you how to use `StringIO` memory files to capture and view stdout.

Couple of things I personally have used it for:

  1. Whole-file caching. I have a script that reads PDFs and does validation of various things about them. The PDF library I'm using takes an open file in its document constructor. I originally just opened the PDF I was interested in reading, however when I changed it to read the entire file at once into memory then pass a StringIO object to the PDF library, the running time of my script was cut in half.

  2. Deferred printing. Same script prints a header before every PDF it reads. However, I can specify on the command line whether to ignore certain tests that are in its configuration file, or to only include certain ones. If I ignore all tests for a given PDF I don't want the header printed, but I won't know how many tests I ran until I'm done running the tests (the tests can be defined dynamically as well). So I capture the header into a StringIO object by changing sys.stdout to point to it, and each time I run a test I check to see whether that object has anything in it. If so, I print it then and reset it to empty. Voila, only PDFs that have tests have headers printed.

What is exactly a file-like object in Python?, It's used when you have some API that only takes files, but you need to use a string. For example, to compress a string using the gzip module in Python 2: Python StringIO.StringIO() Examples. The following are code examples for showing how to use StringIO.StringIO(). They are extracted from open source Python projects. You can vote up the examples you like or vote down the ones you don't like. You can also save this page to your account.

string - What is StringIO in python used for in reality?, The StringIO object can accept either Unicode or 8-bit strings, but mixing the two may take some care. If both are used, 8-bit strings that cannot be interpreted as  À quoi sert en réalité StringIO en python? Je ne suis pas un pro et je me suis gratté la tête pour comprendre à quoi sert exactement StringIO. J'ai été à la recherche autour de l'internet pour quelques exemples.

7.5. StringIO — Read and write strings as files, Home » Python » Python io – BytesIO, StringIO Python io module allows us to manage the Stack Overflow What is StringIO in python used for in reality? Home » Python » Python io – BytesIO, StringIO Python io module allows us to manage the file-related input and output operations. The advantage of using the IO module is that the classes and functions available allows us to extend the functionality to enable writing to the Unicode data.

Python stringio to file, In Python 3, only the iterator version exists but it uses the list-returning name (i.e., In Py2 there are three flavours of StringIO: a pure Python module (StringIO), like _phred_to_ascii* ) that these formats are in fact mixed binary and ASCII,  1 http://stackoverflow.com/questions/7996479/what-is-stringio-in-python-used-for-in-reality StringIO gives you file-like access to strings, so you can use an existing module that deals with a file and change almost nothing and make it work with strings.

Supporting Python 2 and Python 3, Reworking StringIO concatenation in Python CPython can detect that case because it uses reference counts on its objects for garbage collection; PyPy is not The inevitable reality check can be inconvenient. Reworking  In Python 2, a string is just an array of bytes, exactly like the bytes type in Python 3. For a string s you can call s.decode() to get a Unicode string, but you must * pass the encoding manually for exactly that reason.

Comments
  • in other words: duck typing :D
  • Since Python 3.2, the gzip module has functions compress data directly. (But any well-known open-source library that currently needs StringIO will probably grow such functions after some time, so rather than search for a new example I'll leave gzip here.)
  • stringIO is also helpful in writing a file directly into S3 (i.e. without the need to save locally first then upload).
  • I've also found StringIO to be considerably faster if you are dealing with multiple megabytes of character-data when compared to expressions like mystr += "more stuff\n" within a loop, especially if you can use cStringIO.StringIO instead of just io.StringIO.