Task: CSV data manipulation
C: #define TITLE "CSV data manipulation"
#define URL "http:

#define _GNU_SOURCE
#define bool int
#include <stdio.h>
#include <stdlib.h> 
#include <string.h> 
#include <ctype.h>
#include <errno.h>





typedef struct {
	char * delim;
	unsigned int rows;
	unsigned int cols;
	char ** table;
} CSV;



int trim(char ** str) {
	int trimmed;
	int n;
	int len;
	
	len = strlen(*str);
	n = len - 1;
	
	while((n>=0) && isspace((*str)[n])) {
		(*str)[n] = '\0'; 
		trimmed += 1;
		n--;
	}

	
	n = 0;
	while((n < len) && (isspace((*str)[0]))) {
		(*str)[0] = '\0'; 
		*str = (*str)+1;
		trimmed += 1;
		n++;
	}
	return trimmed;
}



int csv_destroy(CSV * csv) {
	if (csv == NULL) { return 0; }
	if (csv->table != NULL) { free(csv->table); }
	if (csv->delim != NULL) { free(csv->delim); }
	free(csv);
	return 0;
}



CSV * csv_create(unsigned int cols, unsigned int rows) {
	CSV * csv;
	
	csv = malloc(sizeof(CSV));
	csv->rows = rows;
	csv->cols = cols;
	csv->delim = strdup(",");

	csv->table = malloc(sizeof(char *) * cols * rows);
	if (csv->table == NULL) { goto error; }

	memset(csv->table, 0, sizeof(char *) * cols * rows);

	return csv;

error:
	csv_destroy(csv);
	return NULL;
}



char * csv_get(CSV * csv, unsigned int col, unsigned int row) {
	unsigned int idx;
	idx = col + (row * csv->cols);
	return csv->table[idx];
}



int csv_set(CSV * csv, unsigned int col, unsigned int row, char * value) {
	unsigned int idx;
	idx = col + (row * csv->cols);
	csv->table[idx] = value;
	return 0;
}

void csv_display(CSV * csv) {
	int row, col;
	char * content;
	if ((csv->rows == 0) || (csv->cols==0)) {
		printf("[Empty table]\n");
		return ;
	}

	printf("\n[Table cols=%d rows=%d]\n", csv->cols, csv->rows);
	for (row=0; row<csv->rows; row++) {
		printf("[|");
		for (col=0; col<csv->cols; col++) {
			content = csv_get(csv, col, row);
            printf("%s\t|", content);
		}
        printf("]\n");
	}
	printf("\n");
}


int csv_resize(CSV * old_csv, unsigned int new_cols, unsigned int new_rows) {
	unsigned int cur_col, 
				 cur_row, 
				 max_cols,
				 max_rows;
	CSV * new_csv;
	char * content;
	bool in_old, in_new;

	
	new_csv = csv_create(new_cols, new_rows);
	if (new_csv == NULL) { goto error; }

	new_csv->rows = new_rows;
	new_csv->cols = new_cols;


	max_cols = (new_cols > old_csv->cols)? new_cols : old_csv->cols;
	max_rows = (new_rows > old_csv->rows)? new_rows : old_csv->rows;

	for (cur_col=0; cur_col<max_cols; cur_col++) {
		for (cur_row=0; cur_row<max_rows; cur_row++) {
			in_old = (cur_col < old_csv->cols) && (cur_row < old_csv->rows);
			in_new = (cur_col < new_csv->cols) && (cur_row < new_csv->rows);

			if (in_old && in_new) {
				
				content = csv_get(old_csv, cur_col, cur_row);
				csv_set(new_csv, cur_col, cur_row, content);
			} else if (in_old) {
				
				content = csv_get(old_csv, cur_col, cur_row);
				free(content);
			} else {  }
		}
	}
			
	free(old_csv->table);
	old_csv->rows = new_rows;
	old_csv->cols = new_cols;
	old_csv->table = new_csv->table;
	new_csv->table = NULL;
	csv_destroy(new_csv);

	return 0;

error:
	printf("Unable to resize CSV table: error %d - %s\n", errno, strerror(errno));
	return -1;
}



int csv_open(CSV * csv, char * filename) {
	FILE * fp;
	unsigned int m_rows;
	unsigned int m_cols, cols;
	char line[2048];
	char * lineptr;
	char * token;


	fp = fopen(filename, "r");
	if (fp == NULL) { goto error; }

	m_rows = 0;
	m_cols = 0;
	while(fgets(line, sizeof(line), fp) != NULL) {
 		m_rows += 1;
 		cols = 0;
 		lineptr = line;
 		while ((token = strtok(lineptr, csv->delim)) != NULL) {
 			lineptr = NULL;
 			trim(&token);
            cols += 1;
        	if (cols > m_cols) { m_cols = cols; }
            csv_resize(csv, m_cols, m_rows);
            csv_set(csv, cols-1, m_rows-1, strdup(token));
        }
	}

	fclose(fp);
	csv->rows = m_rows;
	csv->cols = m_cols;
	return 0;

error:
	fclose(fp);
	printf("Unable to open %s for reading.", filename);
	return -1;
}



int csv_save(CSV * csv, char * filename) {
	FILE * fp;
	int row, col;
	char * content;

	fp = fopen(filename, "w");
	for (row=0; row<csv->rows; row++) {
		for (col=0; col<csv->cols; col++) {
			content = csv_get(csv, col, row);
            fprintf(fp, "%s%s", content, 
            		((col == csv->cols-1) ? "" : csv->delim) );
		}
        fprintf(fp, "\n");
	}

	fclose(fp);
	return 0;
}



int main(int argc, char ** argv) {
	CSV * csv;

	printf("%s\n%s\n\n",TITLE, URL);

	csv = csv_create(0, 0);
	csv_open(csv, "fixtures/csv-data-manipulation.csv");
	csv_display(csv);

	csv_set(csv, 0, 0, "Column0");
	csv_set(csv, 1, 1, "100");
	csv_set(csv, 2, 2, "200");
	csv_set(csv, 3, 3, "300");
	csv_set(csv, 4, 4, "400");
	csv_display(csv);

	csv_save(csv, "tmp/csv-data-manipulation.result.csv");
	csv_destroy(csv);

	return 0;
}

Python: import fileinput

changerow, changecolumn, changevalue = 2, 4, '"Spam"'

with fileinput.input('csv_data_manipulation.csv', inplace=True) as f:
    for line in f:
        if fileinput.filelineno() == changerow:
            fields = line.rstrip().split(',')
            fields[changecolumn-1] = changevalue
            line = ','.join(fields) + '\n'
        print(line, end='')