[Tut] Python Convert String to CSV File

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Python Convert String to CSV File

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Problem Formulation

Given a Python string:

Code:

my_string = '''a,b,c 1,2,3 9,8,7'''

Question: How to convert the string to a CSV file in Python?

The desired output is the CSV file:

Code:

'my_file.csv'

:

Code:

a,b,c 1,2,3 9,8,7

Simple Vanilla Python Solution

To convert a multi-line string with comma-separated values to a CSV file in Python, simply write the string in a file (e.g., with the name

Code:

'my_file.csv'

) without further modification.

This works if the string is already in the correct CSV format with values separated by commas.

The following code uses the

Code:

open()

function and the

Code:

file.write()

functions to write the multi-line string to a file without modification.

Code:

my_string = '''a,b,c 1,2,3 9,8,7''' with open('my_file.csv', 'w') as out: out.write(my_string)

The result is a file

Code:

'my_file.csv'

with the following contents:

Code:

a,b,c 1,2,3 9,8,7

Parsing and Modifying Text to CSV

The string may not be in the correct CSV format.

For example, you may want to convert any of the following strings to a CSV file—their format is not yet ready for writing it directly in a comma-separated file (CSV):

1. Example 1:
   Code:

   'abc;123;987'
   
   
2. Example 2:
   Code:

   'abc 123 987'
   
   
3. Example 3:
   Code:

   'a=b=c 1=2=3 9=8=7'
   
   
4. …
   

To parse such a string and modify it before writing it in a file

Code:

'my_file.csv'

, you can use the

Code:

string.replace()

and

Code:

string.split()

methods to make sure that each value is separated by a comma and each row has its own line.

Let’s go over each of those examples to see how to parse the string effectively to bring it into the CSV format:

Example 1

Code:

# Example 1: my_string = 'abc;123;987' with open('my_file.csv', 'w') as out: lines = [','.join(line) for line in my_string.split(';')] my_string = '\n'.join(lines) out.write(my_string)

I’ve higlighted the two code lines that convert the string to the CSV format.

• The first highlighted line uses list comprehension to create a list of three lines, each interleaved with a comma.
  
  
• The second highlighted line uses the
  Code:

  string.join()
  function to bring those together to a CSV format that can be written into the output file.
  

The output file

Code:

'my_file.csv'

contains the same CSV formatted text:

Code:

a,b,c 1,2,3 9,8,7

Example 2

The following example is the same as the previous code snippet, only that the empty spaces

Code:

' '

in the input string should be converted to new lines to obtain the final CSV:

Code:

# Example 2: my_string = 'abc 123 987' with open('my_file.csv', 'w') as out: lines = [','.join(line) for line in my_string.split(' ')] my_string = '\n'.join(lines) out.write(my_string)

The output file

Code:

'my_file.csv'

contains the same CSV formatted text:

Code:

a,b,c 1,2,3 9,8,7

Example 3

If the comma-separated values are not yet comma-separated (e.g., they may be semicolon-separated

Code:

'a;b;c'

), you can use the

Code:

string.replace()

method to replace the symbols accordingly.

This is shown in the following example:

Code:

# Example 3: my_string = 'a=b=c 1=2=3 9=8=7' with open('my_file.csv', 'w') as out: my_string = my_string.replace('=', ',').replace(' ', '\n') out.write(my_string)

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