Python: Writing to same rows in a CSV file

Question

I have a text file that has numerous lines. I want to extract certain lines and write them to a CSV file. However, I want to write particular lines to the same row in the CSV file. For example, my text file is like this:

Name= Sarah F
Location= Baltimore MD
Name= Bob M
Location= Sacramento CA
Name= Tom M NY
Location= Brooklyn NY
Name= Anne F
Location= Morristown NJ

My CSV file I want to generate will include the name of the person, their sex, the city and state they reside in:

Sarah,F,Baltimore,MD
Bob,M,Sacramento,CA
Tom,M,Brooklyn,NY
Anne,F,Morristown,NJ

When I use csv.writerows([list]) I get the names , sex and the city , state written in separate rows:

Sarah,F
Baltimore,MD
Bob,M
Sacramento,CA
Tom,M
Brooklyn,NY
Anne,F
Morristown,NJ

When I try to append to the list with: [name, sex] the city and state the override the original list instead of appending.

Here is my code to do this:

import csv

file = open("file_to_use.txt", 'r')
csv_file = open("file_to_write.csv", 'wb')
writer = csv.writer(csv_file)

Row_lines =[]

for line in file: 

    if line.startswith("Name="):
        name_line = line.replace(" ", ",")
        name_line = name_line.strip("\n")

        Row_lines.append(name_line)

    if line.startswith("Location="):
        loc_line = line.replace(" ", ",")
        loc_line = loc_line.strip("\n")                

        Row_lines.append(loc_line)

    writer.writerows(Row_lines)

csv_file.close()

I know I have some logical order in the incorrect place, but I can't seem to figure it out.

Answer 1

Each time you call Row_lines.append(), you are adding a new item to the list. Each item in the list is written as a separate line when you call writer.writerows(Row_lines).

Each time you encounter a name line, you should create a new string from that line, but don't add it to the Row_lines list yet. Each time you encounter a location line, you should append it to the name line string, creating a complete row which you can now add to the Row_lines list.

And instead of calling writerows() on each iteration of the loop, you should call it once after you have compiled the full list of rows.

import csv

file = open("file_to_use.txt", 'r')
csv_file = open("file_to_write.csv", 'wb')
writer = csv.writer(csv_file)

Row_lines =[]

for line in file: 

    if line.startswith("Name="):
        name_line = line.replace(" ", ",")
        name_line = name_line.strip("\n")

        # start building the new line
        current_line = name_line

    if line.startswith("Location="):
        loc_line = line.replace(" ", ",")
        loc_line = loc_line.strip("\n")                

        # append the extra fields to the current line
        current_line = current_line + ',' + loc_line

        # add the current line to the output list
        Row_lines.append(current_line)

# call this after you have added
# all lines, not after each one
writer.writerows(Row_lines)

csv_file.close()

Answer 2

您要向Row_lines添加两个不同的行，它们代表一个单独的csv行，您应该仅将一行添加到Row_lines中。

Answer 3

There are two parts to your task. First is joining the rows, you can use zip for that:

with open(inputfile) as propsfile:
    data = [row.split("=")[1].split() for row in propsfile]

# join two at a time
data_tuples = zip(data[::2], data[1::2])

Second is writing the rows, you can use the csv module for that:

import csv
with open(outputfile, 'w') as csvfile:
    writer = csv.writer(csvfile)
    writer.writerows([name+location for name, location in data_tuples])

Now we have the data in outputfile :

Sarah,F,Baltimore,MD
Bob,M,Sacramento,CA
...

Answer 4

Here is a code that does not use any external libraries.

Since all your lines are not necessarily consistent (eg "Name= Tom M NY" - NY should probably not be there), this code looks at the 2 first data entries following "Name=" or "Location=" and ignores any subsequent entries (like "NY" in the example above).

# Opening the file to use
input_file = open(r"C:\Temp\file_to_use.txt", 'r')

# Creating an empty CSV file
output_file = open(r"C:\Temp\output.csv", 'w')

# Going through the text file, it is checking whether the line holds name or location information
# If it holds location information, all saved information so far is saved to the CSV file
for line in input_file:
    line = line.split("=")
    if line[0] == "Name":
        first_name, last_name = line[1].strip().split()[:2]
    elif line[0] == "Location":
        city, state = line[1].strip().split()[:2]
        output_file.write('%s,%s,%s,%s\n' % (first_name, last_name, city, state))

# Closes the opened files
input_file.close()
output_file.close()