Reading and writing a text file

[psbasha]

Hi,

Is it necessary in Python to close the File after reading or writing the data to file?.While refering to Python material ,I saw some where mentioning that no need to close the file.Correct me if I am wrong.

If possible could anybody help me with sample code for reading and writing a simple text file.I have seen there are many ways to read /write the data in Python.But I want to use the effective way of reading or writing the data from and to file.

Thanks in advance
PSB

[bvdet]

Hi,

Is it necessary in Python to close the File after reading or writing the data to file?.While refering to Python material ,I saw some where mentioning that no need to close the file.Correct me if I am wrong.

If possible could anybody help me with sample code for reading and writing a simple text file.I have seen there are many ways to read /write the data in Python.But I want to use the effective way of reading or writing the data from and to file.

Thanks in advance
PSB

This thread shows how to read and write data:http://www.thescripts.com/forum/thre...7166-1-10.html
There are several other theads on file I/O that I have participated in.

Python will close an open file in its garbage collection routine when the file object reference is reassigned or decreases to None. It is good practice to close every file that is opened - especially when a file object was created. This brings up a subject that has puzzled me. Open a file like this:

lineLst = open('file_name').readlines()

Does Python close the file? No file object is created, so the file is closed when the end of file is reached (I think).

[ghostdog74]

This brings up a subject that has puzzled me. Open a file like this:

lineLst = open('file_name').readlines()

Does Python close the file? No file object is created, so the file is closed when the end of file is reached (I think).

yes Python does close the file when the file object gets garbage collected.

[psbasha]

I have a file data in this format

Employee # Employee Name Salary Location
---------------------------------------------------------------------------------------------
121111 Sam 10,000 NJ
121311 Paul 20,000 NY
111111 Jim 10,000 TX

The data is in Xls and we are copying manually into text file.After copying into text file ,the data is not organized as we see in xls.

So how to read this file data (without using slicing concept) and store in the respective fields.

Could anybody provide a sample piece of code.

Thanks
PSB

[bvdet]

I have a file data in this format

Employee # Employee Name Salary Location
---------------------------------------------------------------------------------------------
121111 Sam 10,000 NJ
121311 Paul 20,000 NY
111111 Jim 10,000 TX

The data is in Xls and we are copying manually into text file.After copying into text file ,the data is not organized as we see in xls.

So how to read this file data (without using slicing concept) and store in the respective fields.

Could anybody provide a sample piece of code.

Thanks
PSB

You can save the Excel worksheet as a text file. The text file will be tab delimited which can be easily parsed.

"""
Read a tab delimited file
"""

fn = 'your_file'

f = open(fn, 'r')
labelLst = f.readline().strip().split('\t')
lineLst = []

for line in f:
    if not line.startswith('#'):
        lineLst.append(line.strip().split('\t'))

f.close()

print labelLst
print lineLst

[psbasha]

Could anybody help me in reading this data.How to seperate the line data and read.

SET 10 = 1101 1106 1107 1108 1109 1110 1111,
1112 1113 1114 1115 1116 1117 1118,
1119 1120 1121 1122 1123 1124 1125

If anybody provide a sample code for the above it will be helpful.

Thanks in advance
PSB

[bvdet]

Could anybody help me in reading this data.How to seperate the line data and read.

SET 10 = 1101 1106 1107 1108 1109 1110 1111,
1112 1113 1114 1115 1116 1117 1118,
1119 1120 1121 1122 1123 1124 1125

If anybody provide a sample code for the above it will be helpful.

Thanks in advance
PSB

s = 'SET 10 = 1101 1106 1107 1108 1109 1110 1111,\n 1112 1113 1114 1115 1116 1117 1118,\n 1119 1120 1121 1122 1123 1124 1125'
sList = s.split('=')
label = sList[0].strip()
data = sList[1].strip().split(',\n')
datastr = ''.join(data)

print '%s = %s' % (label, datastr)
'''
>>> SET 10 = 1101 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
'''

[psbasha]

Thanks for the reply,

This is the input file :

$
$ SET 10
$
$ hjdsahclaladsal kjls
$PTITLE = SET 10 = SET_110
SET 10 = 1101 1106 1107 1108 1109 1110 1111,
1112 1113 1114 1115 1116 1117 1118,
1119 1120 1121 1122 1123 1124 1125
$ END OF SET 110
$

I have to get the SET # 10 and all the integers starting from the 1101 to 1125.How can I read all the integer numbers from the 1101 to 1125.

Is it possible with the solution provided by you?.If possible what is the modifications has to be done to that piece of code

[bvdet]

Thanks for the reply,

This is the input file :

$
$ SET 10
$
$ hjdsahclaladsal kjls
$PTITLE = SET 10 = SET_110
SET 10 = 1101 1106 1107 1108 1109 1110 1111,
1112 1113 1114 1115 1116 1117 1118,
1119 1120 1121 1122 1123 1124 1125
$ END OF SET 110
$

I have to get the SET # 10 and all the integers starting from the 1101 to 1125.How can I read all the integer numbers from the 1101 to 1125.

Is it possible with the solution provided by you?.If possible what is the modifications has to be done to that piece of code

This will give you a list of integers from the data string in my earlier post:

map(int, datastr.split())

[psbasha]

I understand the piece of code what you have posted.But how to capture the data in between the Key Words "SET" and "END".My program should be generic enough to read this data in between this key words

SET 10 = 1101 1106 1107 1108 1109 1110 1111,
1112 1113 1114 1115 1116 1117 1118,
1119 1120 1121 1122 1123 1124 1125
$ END OF SET 110

[ghostdog74]

Thanks for the reply,

This is the input file :

$
$ SET 10
$
$ hjdsahclaladsal kjls
$PTITLE = SET 10 = SET_110
SET 10 = 1101 1106 1107 1108 1109 1110 1111,
1112 1113 1114 1115 1116 1117 1118,
1119 1120 1121 1122 1123 1124 1125
$ END OF SET 110
$

I have to get the SET # 10 and all the integers starting from the 1101 to 1125.How can I read all the integer numbers from the 1101 to 1125.

Is it possible with the solution provided by you?.If possible what is the modifications has to be done to that piece of code

another way

>>> import re
>>> data = open("file").read()
>>> re.compile("SET 10 = (\d+.*)\$ END OF SET 110",re.M|re.DOTALL).findall(data)[0].replace("\n","").replace(","," ")
'1101 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125'
>>>

[bvdet]

I understand the piece of code what you have posted.But how to capture the data in between the Key Words "SET" and "END".My program should be generic enough to read this data in between this key words

SET 10 = 1101 1106 1107 1108 1109 1110 1111,
1112 1113 1114 1115 1116 1117 1118,
1119 1120 1121 1122 1123 1124 1125
$ END OF SET 110

Iterate on the file for line in file: Untested:

if line.startswith('SET'):
    in_set = True
    s = line
elif line.startswith('$'):
    in_set = False
elif in_set:
    s += line
return s

[bvdet]

another way

>>> import re
>>> data = open("file").read()
>>> re.compile("SET 10 = (\d+.*)\$ END OF SET 110",re.M|re.DOTALL).findall(data)[0].replace("\n","").replace(","," ")
'1101 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125'
>>>

I like that ghostdog! :)

[psbasha]

another way

>>> import re
>>> data = open("file").read()
>>> re.compile("SET 10 = (\d+.*)\$ END OF SET 110",re.M|re.DOTALL).findall(data)[0].replace("\n","").replace(","," ")
'1101 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125'
>>>

What this piece of code will do ?.I am not able to understand what these piece of code will do ?

[ghostdog74]

What this piece of code will do ?.I am not able to understand what these piece of code will do ?

I will just briefly explain as my english is not good. hope you will understand
The 're' module is regular expression module. More information can be found here at python docs

>>> data = open("file").re ad()

reads in the whole file as a string to be fed to re module's findall() method

>>> re.compile("SET 10 = (\d+.*)\$ END OF SET 110",re.M|re.DO TALL).findall(d ata)[0].replace("\n"," ").replace(",", " ")
'1101 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125'
>>>

you wanted to find the numbers between "SET 10 ="
and "$END OF SET 110" . \d+ means find more that one digits. \d+.* means go on and find more of those digits. by putting brackets between (\d+.*), the results of findall() will return these digit groups. re.compile() sets up the pattern that i want to find and re.M means to search for the pattern in multiline mode. re.DOTALL means to make the "." match a newline. In other words, the "." in (\d+.*) will match newline because your numbers are split into multiline. findall() method will do the searching, and will output the results in one list. In this list, there are redundant \n and "," , so got to get rid of them through replace()

Anyway , this is just another method. I suggest you use bvdet's method if you are not familiar with regular expression.