Develop Reference

Removing white space and colon

I have a file with a bunch of numbers that have white spaces and colons and I am trying to remove them. As I have seen on this forum the function line.strip.split() works well to achieve this. Is there a way of removing the white space and colon all in one go? Using the method posted by Lorenzo I have this:
train = []
with open('C:/Users/Morgan Weiss/Desktop/STA5635/DataSets/dexter/dexter_train.data') as train_data:
train.append(train_data.read().replace(' ','').replace(':',''))
size_of_train = np.shape(train)
for i in range(size_of_train[0]):
for j in range(size_of_train[1]):
train[i][j] = int(train[i][j])
print(train)
Although I get this error:
File "C:/Users/Morgan Weiss/Desktop/STA5635/Homework/Homework_1/HW1_Dexter.py", line 11, in <module>
for j in range(size_of_train[1]):
IndexError: tuple index out of range

I think the above syntax is not correct, but anyways as per your question, you can use replace function present in python.
When reading each line as a string from that file you can do something like,
train = []
with open('/Users/sushant.moon/Downloads/dexter_train.data') as f:
list = f.read().split()
for x in list:
data = x.split(':')
train.append([int(data[0]),int(data[1])])
# this part becomes redundant as i have already converted str to int before i append data to train
size_of_train = np.shape(train)
for i in range(size_of_train[0]):
for j in range(size_of_train[1]):
train[i][j] = int(train[i][j])
Here I am using replace function to replace space with blank string, and similar with colon.

You did not provide an example of what your input file looks like so we can only speculate what solution you need. I'm going to suppose that you need to extract integers from your input text file and print their values.
Here's how I would do it:
Instead of trying to eliminate whitespace characters and colons, I will be searching for digits using a regular expression
Consecutive digits would constitute a number
I would convert this number to an integer form.
And here's how it would look like:
import re
input_filename = "/home/evens/Temporaire/Stack Exchange/StackOverflow/Input_file-39359816.txt"
matcher = re.compile(r"\d+")
with open(input_filename) as input_file:
for line in input_file:
for digits_found in matcher.finditer(line):
number_in_string_form = digits_found.group()
number = int(number_in_string_form)
print(number)
But before you run away with this code, you should continue to learn Python because you don't seem to grasp its basic elements yet.

Python - Splitting a large string by number of delimiter occurrences

I'm still learning Python, and I have a question I haven't been able to solve. I have a very long string (millions of lines long) which I would like to be split into a smaller string length based on a specified number of occurrences of a delimeter.
For instance:
ABCDEF
//
GHIJKLMN
//
OPQ
//
RSTLN
//
OPQR
//
STUVW
//
XYZ
//
In this case I would want to split based on "//" and return a string of all lines before the nth occurrence of the delimeter.
So an input of splitting the string by // by 1 would return:
ABCDEF
an input of splitting the string by // by 2 would return:
ABCDEF
//
GHIJKLMN
an input of splitting the string by // by 3 would return:
ABCDEF
//
GHIJKLMN
//
OPQ
And so on... However, The length of the original 2 million line string appeared to be a problem when I simply tried to split the entire string and by "//" and just work with the individual indexes. (I was getting a memory error) Perhaps Python can't handle so many lines in one split? So I can't do that.
I'm looking for a way that I don't need to split the entire string into a hundred-thousand indexes when I may only need 100, but instead just start from the beginning until a certain point, stop and return everything before it, which I assume may also be faster? I hope my question is as clear as possible.
Is there a simple or elegant way to achieve this? Thanks!

If you want to work with files instead of strings in memory, here is another answer.
This version is written as a function that reads lines and immediately prints them out until the specified number of delimiters have been found (no extra memory needed to store the entire string).
def file_split(file_name, delimiter, n=1):
with open(file_name) as fh:
for line in fh:
line = line.rstrip() # use .rstrip("\n") to only strip newlines
if line == delimiter:
n -= 1
if n <= 0:
return
print line
file_split('data.txt', '//', 3)
You can use this to write the output to a new file like this:
python split.py > newfile.txt
With a little extra work, you can use argparse to pass parameters to the program.

As a more efficient way you can read the firs N lines separated by your delimiter so if you are sure that all of your lines are splitted by delimiter you can use itertools.islice to do the job:
from itertools import islice
with open('filename') as f :
lines = islice(f,0,2*N-1)

The method that comes to my mind when I read your question uses a for loop
where you cut up the string into several (for example the 100 you called) and iterate through the substring.
thestring = "" #your string
steps = 100 #length of the strings you are going to use for iteration
log = 0
substring = thestring[:log+steps] #this is the string you will split and iterate through
thelist = substring.split("//")
for element in thelist:
if(element you want):
#do your thing with the line
else:
log = log+steps
# and go again from the start only with this offset
now you can go through all the elements go through the whole 2 million(!) line string.
best thing to do here is actually make a recursive function from this(if that is what you want):
thestring = "" #your string
steps = 100 #length of the strings you are going to use for iteration
def iterateThroughHugeString(beginning):
substring = thestring[:beginning+steps] #this is the string you will split and iterate through
thelist = substring.split("//")
for element in thelist:
if(element you want):
#do your thing with the line
else:
iterateThroughHugeString(beginning+steps)
# and go again from the start only with this offset

For instance:
i = 0
s = ""
fd = open("...")
for l in fd:
if l[:-1] == delimiter: # skip last '\n'
i += 1
if i >= max_split:
break
s += l
fd.close()

Since you are learning Python it would be a challenge to model a complete dynamic solution. Here's a notion of how you can model one.
Note: The following code snippet only works for file(s) which is/are in the given format (see the 'For Instance' in the question). Hence, it is a static solution.
num = (int(input("Enter delimiter: ")) * 2)
with open("./data.txt") as myfile:
print ([next(myfile) for x in range(num-1)])
Now that have the idea, you can use pattern matching and so on.

Looping a write command to output many different indices from a list separately in Python

Im trying to get an output like:
KPLR003222854-2009131105131
in a text file. The way I am attempting to derive that output is as such:
with open('Processed_Data.txt', 'r') as file_P, open('KIC_list.txt', 'w') as namelist:
nameData = []
for line in file_P:
splt_file_P = line.split()
nameData.append(splt_file_P[0])
for key in nameData:
namelist.write('\n' 'KPLR00' + "".join(str(w) for w in nameData) + '-2009131105131')
However I am having an issue in that the numbers in the nameData array are all appearing at once in the specified output, instead of using on ID cleanly as shown above the output is something like this:
KPLR00322285472138721382172198371823798123781923781237819237894676472634973256279234987-2009131105131
So my question is how do I loop the write command in a way that will allow me to get each separate ID (each has a specific index value, but there are over 150) to be properly outputted.
EDIT:
Also, some of the ID's in the list are not the same length, so I wanted to add 0's to the front of the 'key' to make them all equal 9 digits. I cheated this by adding the 0's into the KPLR in quotes but not all of the ID's need just two 0's. The question is, could I add 0's between KPLR and the key in any way to match the 9-digit format?

Your code looks like it's working as one would expect: "".join(str(w) for w in nameData) makes a string composed of the concatenation of every item in nameData.
Chances are you want;
for key in nameData:
namelist.write('\n' 'KPLR00' + key + '-2009131105131')
Or even better:
for key in nameData:
namelist.write('\nKPLR%09i-2009131105131'%int(key)) #no string concatenation
String concatenation tends to be slower, and if you're not only operating on strings, will involve explicit calls to str. Here's a pair of ideone snippets showing the difference: http://ideone.com/RR5RnL and http://ideone.com/VH2gzx
Also, the above form with the format string '%09i' will pad with 0s to make the number up to 9 digits. Because the format is '%i', I've added an explicit conversion to int. See here for full details: http://docs.python.org/2/library/stdtypes.html#string-formatting-operations
Finally, here's a single line version (excepting the with statement, which you should of course keep):
namelist.write("\n".join("KPLR%09i-2009131105131"%int(line.split()[0]) for line in file_P))

You can change this:
"".join(str(w) for w in nameData)
to this:
",".join(str(w) for w in nameData)
Basically, the "," will comma delimit the elements in your nameData list. If you use "", then there will be nothing to separate the elements, so they appear all at once. You can change the delimiter to suit your needs.

Just for kicks:
with open('Processed_Data.txt', 'r') as file_P, open('KIC_list.txt', 'w') as namelist:
nameData = [line.split()[0] for line in file_P]
namelist.write("\n".join("KPLR00" + str(key) + '-2009131105131' for key in nameData))
I think that will work, but I haven't tested it. You can make it even smaller/uglier by not using nameData at all, and just use that list comprehension right in its place.

Increment a Version Number using Regular Expression

I am trying to increment a version number using regex but I can't seem to get the hang of regex at all. I'm having trouple with the symbols in the string I am trying to read and change. The code I have so far is:
version_file = "AssemblyInfo.cs"
read_file = open(version_file).readlines()
write_file = open(version_file, "w")
r = re.compile(r'(AssemblyFileVersion\s*(\s*"\s*)(\S+))\s*"\s*')
for l in read_file:
m1 = r.match(l)
if m1:
VERSION_ID=map(int,m1.group(2).split("."))
VERSION_ID[2]+=1 # increment version
l = r.sub(r'\g<1>' + '.'.join(['%s' % (v) for v in VERSION_ID]), l)
write_file.write(l)
write_file.close()
The string I am trying to read and change is:
[assembly: AssemblyFileVersion("1.0.0.0")]
What I would like written to the file is:
[assembly: AssemblyFileVersion("1.0.0.1")]
So basically I want to increment the build number by one.
Can anyone help me fix my regualr expression. I seem to have trouble getting to grips with regular expression that have to get around symbols.
Thanks for any help.

If you specify the version as "1.0.0.*" then AFAIK it gets updated on each build automagically, at least if you're using Visual Studio.NET.
I'm not sure regex is your best bet, but one way of doing it would be this:
import re
# Don't bother matching everything, just the bits that matter.
pat = re.compile(r'AssemblyFileVersion.*\.(\d+)"')
# ... lines omitted which set up read_file, write_file etc.
for line in read_file:
m = pat.search(line)
if m:
start, end = m.span(1)
line = line[:start] + str(int(line[start:end]) + 1) + line[end:]
write_file.write(line)

Good luck with regex.
If I had to do the same, I'd convert the string to int by removing the dots, add one and convert back to string.
Well, I'd have also used a integer version number in the first place.

Workarounds when a string is too long for a .join. OverflowError occurs

I'm working through some python problems on pythonchallenge.com to teach myself python and I've hit a roadblock, since the string I am to be using is too large for python to handle. I receive this error:
my-macbook:python owner1$ python singleoccurrence.py
Traceback (most recent call last):
File "singleoccurrence.py", line 32, in <module>
myString = myString.join(line)
OverflowError: join() result is too long for a Python string
What alternatives do I have for this issue? My code looks like such...
#open file testdata.txt
#for each character, check if already exists in array of checked characters
#if so, skip.
#if not, character.count
#if count > 1, repeat recursively with first character stripped off of page.
# if count = 1, add to valid character array.
#when string = 0, print valid character array.
valid = []
checked = []
myString = ""
def recursiveCount(bigString):
if len(bigString) == 0:
print "YAY!"
return valid
myChar = bigString[0]
if myChar in checked:
return recursiveCount(bigString[1:])
if bigString.count(myChar) > 1:
checked.append(myChar)
return recursiveCount(bigString[1:])
checked.append(myChar)
valid.append(myChar)
return recursiveCount(bigString[1:])
fileIN = open("testdata.txt", "r")
line = fileIN.readline()
while line:
line = line.strip()
myString = myString.join(line)
line = fileIN.readline()
myString = recursiveCount(myString)
print "\n"
print myString

string.join doesn't do what you think. join is used to combine a list of words into a single string with the given seperator. Ie:
>>> ",".join(('foo', 'bar', 'baz'))
'foo,bar,baz'
The code snippet you posted will attempt to insert myString between every character in the variable line. You can see how that will get big quickly :-). Are you trying to read the entire file into a single string, myString? If so, the way you want to concatenate the strings is like this:
myString = myString + line
While I'm here... since you're learning Python here are some other suggestions.
There are easier ways to read an entire file into a variable. For instance:
fileIN = open("testdata.txt", "r")
myString = fileIN.read()
(This won't have the exact behaviour of your existing strip() code, but may in fact do what you want.)
Also, I would never recommend practical Python code use recursion to iterate over a string. Your code will make a function call (and a stack entry) for every character in the string. Also I'm not sure Python will be very smart about all the uses of bigString[1:]: it may well create a second string in memory that's a copy of the original without the first character. The simplest way to process every character in a string is:
for mychar in bigString:
... do your stuff ...
Finally, you are using the list named "checked" to see if you've ever seen a particular character before. But the membership test on lists ("if myChar in checked") is slow. In Python you're better off using a dictionary:
checked = {}
...
if not checked.has_key(myChar):
checked[myChar] = True
...
This exercise you're doing is a great way to learn several Python idioms.