Featured Post

SQL Query: 3 Methods for Calculating Cumulative SUM

Image
SQL provides various constructs for calculating cumulative sums, offering flexibility and efficiency in data analysis. In this article, we explore three distinct SQL queries that facilitate the computation of cumulative sums. Each query leverages different SQL constructs to achieve the desired outcome, catering to diverse analytical needs and preferences. Using Window Functions (e.g., PostgreSQL, SQL Server, Oracle) SELECT id, value, SUM(value) OVER (ORDER BY id) AS cumulative_sum  FROM your_table; This query uses the SUM() window function with the OVER clause to calculate the cumulative sum of the value column ordered by the id column. Using Subqueries (e.g., MySQL, SQLite): SELECT t1.id, t1.value, SUM(t2.value) AS cumulative_sum FROM your_table t1 JOIN your_table t2 ON t1.id >= t2.id GROUP BY t1.id, t1.value ORDER BY t1.id; This query uses a self-join to calculate the cumulative sum. It joins the table with itself, matching rows where the id in the first table is greater than or

3 Best Methods to Read Files in Python

Read file line by line

Python supports three specific methods to read files- read, readline, readlines. All these you use on files. Each has its unique purpose. Below are the best examples.

3 Methods to read file

  1. read
  2. readline
  3. readlines

Method-1: read

It reads records from file in sequence.

Here, file.txt is sample file with single row.

file.txt


abcdefghijk

file_object.read(2) ==> you will get 'ab'

file_object.read(4)  ===> you will get 'cdef'


Here, the multiple read methods read the data in sequence. The read(x) method will read only the number of characters that mentioned in the read method. Again, if you give multiple read methods then it will read in sequence.


Method-2: readline


It reads the file line by line.

Here, file.txt is a file with single row.

file.txt

abcdefghijk

file_object.readline() ==> you will get 'abcdefghijk'

Here, it reads the file line by line.


Method-3: readlines

It reads all the records at a time.

Here, file.txt is a file with two rows.

file.txt

abcdefghijk
iiiooooooia

file_object.readlines() ==> you will get both the lines.


abcdefghijk
iiiooooooia

Here, it reads all the lines at a time.

Summary

  • I've demonstrated three methods
  • Useful for interviews and projects

Comments

Popular posts from this blog

How to Fix datetime Import Error in Python Quickly

Explained Ideal Structure of Python Class

How to Check Kafka Available Brokers