How to use StringIO in Python3?
PythonPython 3.xIoPython Problem Overview
I am using Python 3.2.1 and I can't import the StringIO
module. I use
io.StringIO
and it works, but I can't use it with numpy
's genfromtxt
like this:
x="1 3\n 4.5 8"
numpy.genfromtxt(io.StringIO(x))
I get the following error:
TypeError: Can't convert 'bytes' object to str implicitly
and when I write import StringIO
it says
ImportError: No module named 'StringIO'
Python Solutions
Solution 1 - Python
> when i write import StringIO it says there is no such module.
From What’s New In Python 3.0:
> The StringIO
and cStringIO
modules are gone. Instead, import the io
> module and use io.StringIO
or io.BytesIO
for text and data
> respectively.
.
A possibly useful method of fixing some Python 2 code to also work in Python 3 (caveat emptor):
try:
from StringIO import StringIO ## for Python 2
except ImportError:
from io import StringIO ## for Python 3
> Note: This example may be tangential to the main issue of the question and is included only as something to consider when generically addressing the missing StringIO
module. For a more direct solution the message TypeError: Can't convert 'bytes' object to str implicitly
, see this answer.
Solution 2 - Python
In my case I have used:
from io import StringIO
Solution 3 - Python
On Python 3 numpy.genfromtxt
expects a bytes stream. Use the following:
numpy.genfromtxt(io.BytesIO(x.encode()))
Solution 4 - Python
Thank you OP for your question, and Roman for your answer. I had to search a bit to find this; I hope the following helps others.
Python 2.7
See: https://docs.scipy.org/doc/numpy/user/basics.io.genfromtxt.html
import numpy as np
from StringIO import StringIO
data = "1, abc , 2\n 3, xxx, 4"
print type(data)
"""
<type 'str'>
"""
print '\n', np.genfromtxt(StringIO(data), delimiter=",", dtype="|S3", autostrip=True)
"""
[['1' 'abc' '2']
['3' 'xxx' '4']]
"""
print '\n', type(data)
"""
<type 'str'>
"""
print '\n', np.genfromtxt(StringIO(data), delimiter=",", autostrip=True)
"""
[[ 1. nan 2.]
[ 3. nan 4.]]
"""
Python 3.5:
import numpy as np
from io import StringIO
import io
data = "1, abc , 2\n 3, xxx, 4"
#print(data)
"""
1, abc , 2
3, xxx, 4
"""
#print(type(data))
"""
<class 'str'>
"""
#np.genfromtxt(StringIO(data), delimiter=",", autostrip=True)
# TypeError: Can't convert 'bytes' object to str implicitly
print('\n')
print(np.genfromtxt(io.BytesIO(data.encode()), delimiter=",", dtype="|S3", autostrip=True))
"""
[[b'1' b'abc' b'2']
[b'3' b'xxx' b'4']]
"""
print('\n')
print(np.genfromtxt(io.BytesIO(data.encode()), delimiter=",", autostrip=True))
"""
[[ 1. nan 2.]
[ 3. nan 4.]]
"""
Aside:
dtype="|Sx", where x = any of { 1, 2, 3, ...}:
https://stackoverflow.com/questions/14790130/dtypes-difference-between-s1-and-s2-in-python
"The |S1 and |S2 strings are data type descriptors; the first means the array holds strings of length 1, the second of length 2. ..."
Solution 5 - Python
You can use the StringIO from the six module:
import six
import numpy
x = "1 3\n 4.5 8"
numpy.genfromtxt(six.StringIO(x))
Solution 6 - Python
Roman Shapovalov's code should work in Python 3.x as well as Python 2.6/2.7. Here it is again with the complete example:
import io
import numpy
x = "1 3\n 4.5 8"
numpy.genfromtxt(io.BytesIO(x.encode()))
Output:
array([[ 1. , 3. ],
[ 4.5, 8. ]])
Explanation for Python 3.x:
numpy.genfromtxt
takes a byte stream (a file-like object interpreted as bytes instead of Unicode).io.BytesIO
takes a byte string and returns a byte stream.io.StringIO
, on the other hand, would take a Unicode string and and return a Unicode stream.x
gets assigned a string literal, which in Python 3.x is a Unicode string.encode()
takes the Unicode stringx
and makes a byte string out of it, thus givingio.BytesIO
a valid argument.
The only difference for Python 2.6/2.7 is that x
is a byte string (assuming from __future__ import unicode_literals
is not used), and then encode()
takes the byte string x
and still makes the same byte string out of it. So the result is the same.
Since this is one of SO's most popular questions regarding StringIO
, here's some more explanation on the import statements and different Python versions.
Here are the classes which take a string and return a stream:
io.BytesIO
(Python 2.6, 2.7, and 3.x) - Takes a byte string. Returns a byte stream.io.StringIO
(Python 2.6, 2.7, and 3.x) - Takes a Unicode string. Returns a Unicode stream.StringIO.StringIO
(Python 2.x) - Takes a byte string or Unicode string. If byte string, returns a byte stream. If Unicode string, returns a Unicode stream.cStringIO.StringIO
(Python 2.x) - Faster version ofStringIO.StringIO
, but can't take Unicode strings which contain non-ASCII characters.
Note that StringIO.StringIO
is imported as from StringIO import StringIO
, then used as StringIO(...)
. Either that, or you do import StringIO
and then use StringIO.StringIO(...)
. The module name and class name just happen to be the same. It's similar to datetime
that way.
What to use, depending on your supported Python versions:
-
If you only support Python 3.x: Just use
io.BytesIO
orio.StringIO
depending on what kind of data you're working with. -
If you support both Python 2.6/2.7 and 3.x, or are trying to transition your code from 2.6/2.7 to 3.x: The easiest option is still to use
io.BytesIO
orio.StringIO
. AlthoughStringIO.StringIO
is flexible and thus seems preferred for 2.6/2.7, that flexibility could mask bugs that will manifest in 3.x. For example, I had some code which usedStringIO.StringIO
orio.StringIO
depending on Python version, but I was actually passing a byte string, so when I got around to testing it in Python 3.x it failed and had to be fixed.Another advantage of using
io.StringIO
is the support for universal newlines. If you pass the keyword argumentnewline=''
intoio.StringIO
, it will be able to split lines on any of\n
,\r\n
, or\r
. I found thatStringIO.StringIO
would trip up on\r
in particular.Note that if you import
BytesIO
orStringIO
fromsix
, you getStringIO.StringIO
in Python 2.x and the appropriate class fromio
in Python 3.x. If you agree with my previous paragraphs' assessment, this is actually one case where you should avoidsix
and just import fromio
instead. -
If you support Python 2.5 or lower and 3.x: You'll need
StringIO.StringIO
for 2.5 or lower, so you might as well usesix
. But realize that it's generally very difficult to support both 2.5 and 3.x, so you should consider bumping your lowest supported version to 2.6 if at all possible.
Solution 7 - Python
In order to make examples from here work with Python 3.5.2, you can rewrite as follows :
import io
data =io.BytesIO(b"1, 2, 3\n4, 5, 6")
import numpy
numpy.genfromtxt(data, delimiter=",")
The reason for the change may be that the content of a file is in data (bytes) which do not make text until being decoded somehow. genfrombytes
may be a better name than genfromtxt
.
Solution 8 - Python
Here is another example for Python 3. It will use two functions to add two numbers and then use CProfile to save the .prof
file. Then it will load the save file using pstats.Stats
and ```StringIO`` to convert the data to a string for further usage.
main.py
import cProfile
import time
import pstats
from io import StringIO
def add_slow(a, b):
time.sleep(0.5)
return a+b
def add_fast(a, b):
return a+b
prof = cProfile.Profile()
def main_func():
arr = []
prof.enable()
for i in range(10):
if i%2==0:
arr.append(add_slow(i,i))
else:
arr.append(add_fast(i,i))
prof.disable()
#prof.print_stats(sort='time')
prof.dump_stats("main_funcs.prof")
return arr
main_func()
stream = StringIO();
stats = pstats.Stats("main_funcs.prof", stream=stream);
stats.print_stats()
stream.seek(0)
print(16*'=',"RESULTS",16*'=')
print (stream.read())
Usage:
python3 main.py
Output:
================ RESULTS ================
Tue Jul 6 17:36:21 2021 main_funcs.prof
26 function calls in 2.507 seconds
Random listing order was used
ncalls tottime percall cumtime percall filename:lineno(function)
10 0.000 0.000 0.000 0.000 {method 'append' of 'list' objects}
5 2.507 0.501 2.507 0.501 {built-in method time.sleep}
5 0.000 0.000 2.507 0.501 profiler.py:39(add_slow)
5 0.000 0.000 0.000 0.000 profiler.py:43(add_fast)
1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects}
Comments: We can observe that in the above code, the time.sleep function is taking about 2.507 seconds.
Solution 9 - Python
I hope this will meet your requirement
import PyPDF4
import io
pdfFile = open(r'test.pdf', 'rb')
pdfReader = PyPDF4.PdfFileReader(pdfFile)
pageObj = pdfReader.getPage(1)
pagetext = pageObj.extractText()
for line in io.StringIO(pagetext):
print(line)