I am new to Python.
Scenario:
apple=gravity search this pattern in file
search for apple if exist fetch corresponding value for apple,
if it is apple=gravity then case pass .
file structure (test.txt )
car=stop
green=go
apple=gravity
Please provide some suggestions as to how I can search value for key in file using Python
Sample:
f = open('test.txt', 'r')
wordCheck="apple=gravity";
for line in f:
if 'wordCheck' == line:
print ('found')
else:
print ('notfound')
break
Split your line with =
Check if apple is present in your first index! If true then, print the second index!
Note:
While reading lines from file, the '\n' character will be present. To get your line without \n read you content from file and use splitlines()!
To make it clean, strip the spaces from the beginning and end of your line to avoid glitches caused by spaces at the beginning and end of your line!
That is,
f = open('test.txt', 'r')
for line in map(str.strip,f.read().splitlines()):
line = line.split('=')
if 'apple' == line[0]:
print line[1]
else:
print ('notfound')
Output:
notfound
notfound
gravity
Hope it helps!
Iterating through the file directly as you are doing, is just fine, and considered more 'Pythonic' than readlines() (or indeed read().splitlines()).
Here, I strip the newline from each line and then split by the = to get the two halves.
Then, I test for the check word, and if present print out the other half of the line.
Note also that I have used the with context manager to open the file. This makes sure that the file is closed, even if an exception occurs.
with open('test.txt', 'r') as f:
wordcheck="apple"
for line in f:
key, val = line.strip().split('=')
if wordcheck == key:
print (val)
else:
print ('notfound')
Related
I have file contains text like Hello:World
#!/usr/bin/python
f = open('m.txt')
while True:
line = f.readline()
if not line :
break
first = line.split(':')[0]
second = line.split(':')[1]
f.close()
I want to put the string after splitting it into 2 variables
On the second iteration i get error
List index out of range
it doesn't break when the line is empty , i searched the answer on related topics and the solution was
if not line:
print break
But it does not work
If there's lines after an empty line (or your text editor inserted an empty line at the end of the file), it's not actually empty. It has a new line character and/or carriage return
You need to strip it off
with open('m.txt') as f:
for line in f:
if not line.strip():
break
first, second = line.split(':')
You can do this relatively easily by utilizing an optional feature of the built-in iter() function by passing it a second argument (called sentinel in the docs) that will cause it to stop if the value is encountered while iterating.
Here's what how use it to make the line processing loop terminate if an empty line is encountered:
with open('m.txt') as fp:
for line in iter(fp.readline, ''):
first, second = line.rstrip().split(':')
print(first, second)
Note the rstrip() which removes the newline at the end of each line read.
Your code is fine, I can't put a picture in a comment. It all works, here:
I've attempted to find this but I end up finding code that replaces that one specific word.
I've been using this code:
phrase = open(club, 'a')
for line in phrase:
if line.contains(name):
#what do i put here?
else:
pass
else:
pass
so lets say I have a text file which contains sam 10 and I want to replace this with sam 5. If I were to do this with the above code how would I? The name will stay the same but the number will not. Since the number is different to each name I'll be unable to search for the number which is why I'm searching for the name. I was thinking of using line.replace but that only changes the one phrase whereas I would want the whole line to change.
Edit: This would be made under the assumption that the text file has multiple names of different people with different numbers. I would want it to search for that specific name and replace the whole line.
Thanks!
You can check line by line to modify and modify the original to save changes:
f = open('sample.txt', 'r')
lines = f.readlines()
f.close()
name = 'ali'
for i in range(len(lines) - 1):
line = lines[i]
#Find 'name' index (-1 if not found)
index = line.find(name)
# If the wanted name is found
if index != -1:
#Split line by spaces to get name and number starting from name
words = line[index:].split()
# Name and number should be the first two elements in words list
name_number = words[0]+ ' ' + '5' #words[1]
#
# Do some thing with name_number
#
# the last '1' is to skip copying a space
line = line[:index] + name_number + ' ' + line[index + len(name_number) + 1:]
# Save result
lines[i] = line
output = open('sample.txt', 'w')
for line in lines:
output.write(line)
output.close()
In general, there are many ways, one of them would be:
Using built-in method:
with open(club, 'r') as in_file, open('new_file', 'w') as out_file:
for line in in_file:
if name in line:
out_file.write(new_line)
else:
out_file.write(line)
But this has the effect of creating a new file.
EDIT:
If you want to do inplace replacement, then you can use fileinput module, this way:
for line in fileinput.input(club, inplace=True):
if name in line:
line = 'NEW LINE' #Construct your new line here
print(line) #This will print it into the file
else:
print(line) #No Changes to be made, print line into the file as it is
Quoting from docs:
class fileinput.FileInput(files=None, inplace=False, backup='', bufsize=0, mode='r', openhook=None)
...
Optional in-place filtering:
if the keyword argument inplace=True is passed to fileinput.input() or
to the FileInput constructor, the file is moved to a backup file and
standard output is directed to the input file (if a file of the same
name as the backup file already exists, it will be replaced silently).
This makes it possible to write a filter that rewrites its input file
in place.
I am trying to read in every line in a file that starts with an 'X:'. I don't want to read the 'X:' itself just the rest of the line that follows.
with open("hnr1.abc","r") as file: f = file.read()
id = []
for line in f:
if line.startswith("X:"):
id.append(f.line[2:])
print(id)
It doesn't have any errors but it doesn't print anything out.
try this:
with open("hnr1.abc","r") as fi:
id = []
for ln in fi:
if ln.startswith("X:"):
id.append(ln[2:])
print(id)
dont use names like file or line
note the append just uses the item name not as part of the file
by pre-reading the file into memory the for loop was accessing the data by character not by line
for line in f:
search = line.split
if search[0] = "X":
storagearray.extend(search)
That should give you an array of all the lines you want, but they'll be split into separate words. Also, you'll need to have defined storagearray before we call it in the above block of code. It's an inelegant solution, as I'm a learner myself, but it should do the job!
edit: If you want to output the lines, simply use python's inbuilt print function:
str(storagearray)
print storagearray
Read every line in the file (for loop)
Select lines that contains X:
Slice the line with index 0: with starting char's/string as X: = ln[0:]
Print lines that begins with X:
for ln in input_file:
if ln.startswith('X:'):
X_ln = ln[0:]
print (X_ln)
Hopefully this is an easy fix. I'm trying to edit one field of a file we use for import, however when I run the following code it leaves the file blank and 0kb. Could anyone advise what I'm doing wrong?
import re #import regex so we can use the commands
name = raw_input("Enter filename:") #prompt for file name, press enter to just open test.nhi
if len(name) < 1 : name = "test.nhi"
count = 0
fhand = open(name, 'w+')
for line in fhand:
words = line.split(',') #obtain individual words by using split
words[34] = re.sub(r'\D', "", words[34]) #remove non-numeric chars from string using regex
if len(words[34]) < 1 : continue # If the 34th field is blank go to the next line
elif len(words[34]) == 2 : "{0:0>3}".format([words[34]]) #Add leading zeroes depending on the length of the field
elif len(words[34]) == 3 : "{0:0>2}".format([words[34]])
elif len(words[34]) == 4 : "{0:0>1}".format([words[34]])
fhand.write(words) #write the line
fhand.close() # Close the file after the loop ends
I have taken below text in 'a.txt' as input and modified your code. Please check if it's work for you.
#Intial Content of a.txt
This,program,is,Java,program
This,program,is,12Python,programs
Modified code as follow:
import re
#Reading from file and updating values
fhand = open('a.txt', 'r')
tmp_list=[]
for line in fhand:
#Split line using ','
words = line.split(',')
#Remove non-numeric chars from 34th string using regex
words[3] = re.sub(r'\D', "", words[3])
#Update the 3rd string
# If the 3rd field is blank go to the next line
if len(words[3]) < 1 :
#Removed continue it from here we need to reconstruct the original line and write it to file
print "Field empty.Continue..."
elif len(words[3]) >= 1 and len(words[3]) < 5 :
#format won't add leading zeros. zfill(5) will add required number of leading zeros depending on the length of word[3].
words[3]=words[3].zfill(5)
#After updating 3rd value in words list, again creating a line out of it.
tmp_str = ",".join(words)
tmp_list.append(tmp_str)
fhand.close()
#Writing to same file
whand = open("a.txt",'w')
for val in tmp_list:
whand.write(val)
whand.close()
File content after running code
This,program,is,,program
This,program,is,00012,programs
The file mode 'w+' Truncates your file to 0 bytes, so you'll only be able to read lines that you've written.
Look at Confused by python file mode "w+" for more information.
An idea would be to read the whole file first, close it, and re-open it to write files in it.
Not sure which OS you're on but I think reading and writing to the same file has undefined behaviour.
I guess internally the file object holds the position (try fhand.tell() to see where it is). You could probably adjust it back and forth as you went using fhand.seek(last_read_position) but really that's asking for trouble.
Also, I'm not sure how the script would ever end as it would end up reading the stuff it had just written (in a sort of infinite loop).
Best bet is to read the entire file first:
with open(name, 'r') as f:
lines = f.read().splitlines()
with open(name, 'w') as f:
for l in lines:
# ....
f.write(something)
For 'Printing to a file via Python' you can use:
ifile = open("test.txt","r")
print("Some text...", file = ifile)
So, basically, I need a program that opens a .dat file, checks each line to see if it meets certain prerequisites, and if they do, copy them into a new csv file.
The prerequisites are that it must 1) contain "$W" or "$S" and 2) have the last value at the end of the line of the DAT say one of a long list of acceptable terms. (I can simply make-up a list of terms and hardcode them into a list)
For example, if the CSV was a list of purchase information and the last item was what was purchased, I only want to include fruit. In this case, the last item is an ID Tag, and I only want to accept a handful of ID Tags, but there is a list of about 5 acceptable tags. The Tags have very veriable length, however, but they are always the last item in the list (and always the 4th item on the list)
Let me give a better example, again with the fruit.
My original .DAT might be:
DGH$G$H $2.53 London_Port Gyro
DGH.$WFFT$Q5632 $33.54 55n39 Barkdust
UYKJ$S.52UE $23.57 22#3 Apple
WSIAJSM_33$4.FJ4 $223.4 Ha25%ek Banana
Only the line: "UYKJ$S $23.57 22#3 Apple" would be copied because only it has both 1) $W or $S (in this case a $S) and 2) The last item is a fruit. Once the .csv file is made, I am going to need to go back through it and replace all the spaces with commas, but that's not nearly as problematic for me as figuring out how to scan each line for requirements and only copy the ones that are wanted.
I am making a few programs all very similar to this one, that open .dat files, check each line to see if they meet requirements, and then decides to copy them to the new file or not. But sadly, I have no idea what I am doing. They are all similar enough that once I figure out how to make one, the rest will be easy, though.
EDIT: The .DAT files are a few thousand lines long, if that matters at all.
EDIT2: The some of my current code snippets
Right now, my current version is this:
def main():
#NewFile_Loc = C:\Users\J18509\Documents
OldFile_Loc=raw_input("Input File for MCLG:")
OldFile = open(OldFile_Loc,"r")
OldText = OldFile.read()
# for i in range(0, len(OldText)):
# if (OldText[i] != " "):
# print OldText[i]
i = split_line(OldText)
if u'$S' in i:
# $S is in the line
print i
main()
But it's very choppy still. I'm just learning python.
Brief update: the server I am working on is down, and might be for the next few hours, but I have my new code, which has syntax errors in it, but here it is anyways. I'll update again once I get it working. Thanks a bunch everyone!
import os
NewFilePath = "A:\test.txt"
Acceptable_Values = ('Apple','Banana')
#Main
def main():
if os.path.isfile(NewFilePath):
os.remove(NewFilePath)
NewFile = open (NewFilePath, 'w')
NewFile.write('Header 1,','Name Header,','Header 3,','Header 4)
OldFile_Loc=raw_input("Input File for Program:")
OldFile = open(OldFile_Loc,"r")
for line in OldFile:
LineParts = line.split()
if (LineParts[0].find($W)) or (LineParts[0].find($S)):
if LineParts[3] in Acceptable_Values:
print(LineParts[1], ' is accepted')
#This Line is acceptable!
NewFile.write(LineParts[1],',',LineParts[0],',',LineParts[2],',',LineParts[3])
OldFile.close()
NewFile.close()
main()
There are two parts you need to implement: First, read a file line by line and write lines meeting a specific criteria. This is done by
with open('file.dat') as f:
for line in f:
stripped = line.strip() # remove '\n' from the end of the line
if test_line(stripped):
print stripped # Write to stdout
The criteria you want to check for are implemented in the function test_line. To check for the occurrence of "$W" or "$S", you can simply use the in-Operator like
if not '$W' in line and not '$S' in line:
return False
else:
return True
To check, if the last item in the line is contained in a fixed list, first split the line using split(), then take the last item using the index notation [-1] (negative indices count from the end of a sequence) and then use the in operator again against your fixed list. This looks like
items = line.split() # items is an array of strings
last_item = items[-1] # take the last element of the array
if last_item in ['Apple', 'Banana']:
return True
else:
return False
Now, you combine these two parts into the test_line function like
def test_line(line):
if not '$W' in line and not '$S' in line:
return False
items = line.split() # items is an array of strings
last_item = items[-1] # take the last element of the array
if last_item in ['Apple', 'Banana']:
return True
else:
return False
Note that the program writes the result to stdout, which you can easily redirect. If you want to write the output to a file, have a look at Correct way to write line to file in Python
inlineRequirements = ['$W','$S']
endlineRequirements = ['Apple','Banana']
inputFile = open(input_filename,'rb')
outputFile = open(output_filename,'wb')
for line in inputFile.readlines():
line = line.strip()
#trailing and leading whitespace has been removed
if any(req in line for req in inlineRequirements):
#passed inline requirement
lastWord = line.split(' ')[-1]
if lastWord in endlineRequirements:
#passed endline requirement
outputFile.write(line.replace(' ',','))
#replaced spaces with commas and wrote to file
inputFile.close()
outputFile.close()
tags = ['apple', 'banana']
match = ['$W', '$S']
OldFile_Loc=raw_input("Input File for MCLG:")
OldFile = open(OldFile_Loc,"r")
for line in OldFile.readlines(): # Loop through the file
line = line.strip() # Remove the newline and whitespace
if line and not line.isspace(): # If the line isn't empty
lparts = line.split() # Split the line
if any(tag.lower() == lparts[-1].lower() for tag in tags) and any(c in line for c in match):
# $S or $W is in the line AND the last section is in tags(case insensitive)
print line
import re
list_of_fruits = ["Apple","Bannana",...]
with open('some.dat') as f:
for line in f:
if re.findall("\$[SW]",line) and line.split()[-1] in list_of_fruits:
print "Found:%s" % line
import os
NewFilePath = "A:\test.txt"
Acceptable_Values = ('Apple','Banana')
#Main
def main():
if os.path.isfile(NewFilePath):
os.remove(NewFilePath)
NewFile = open (NewFilePath, 'w')
NewFile.write('Header 1,','Name Header,','Header 3,','Header 4)
OldFile_Loc=raw_input("Input File for Program:")
OldFile = open(OldFile_Loc,"r")
for line in OldFile:
LineParts = line.split()
if (LineParts[0].find(\$W)) or (LineParts[0].find(\$S)):
if LineParts[3] in Acceptable_Values:
print(LineParts[1], ' is accepted')
#This Line is acceptable!
NewFile.write(LineParts[1],',',LineParts[0],',',LineParts[2],',',LineParts[3])
OldFile.close()
NewFile.close()
main()
This worked great, and has all the capabilities I needed. The other answers are good, but none of them do 100% of what I needed like this one does.