Python sort csv by date

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python sort csv by date

Remember me. Thread Rating: 0 Vote s - 0 Average 1 2 3 4 5. Thread Modes. Sorting csv or txt file on date and time. AshBax Programmer named Tim.

python sort csv by date

Hi, I'm trying to sort a large txt file on 2 columns: date and then time: I've enclosed a small sample of this: 1,2,3,4,5,6,7,8,9,10 ,1,0,, ,1,0,, ,1,0,, ,1,0,, The list above is in the correct order I am looking for This is tested with attached csv file I purposely messed up order of input file to test. Wow - thank you so much that works perfectly.

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Python DateTime, TimeDelta, Strftime(Format) with Examples

Lost Password? AshBax Programmer named Tim Posts: 10 Threads: 3 Joined: Nov Reputation: 0 Likes received: 0 1 Mar, AM Hi, I'm trying to sort a large txt file on 2 columns: date and then time: I've enclosed a small sample of this: 1,2,3,4,5,6,7,8,9,10 ,1,0,, ,1,0,, ,1,0,, ,1,0,, The list above is in the correct order I am looking for Edited 1 time in total.

Always nice to have alternatives Find Quote.Given a list of dates in string format, write a Python program to sort the list of dates in ascending order. Approach: In Python, we can use sort for in-place sorting and sorted returns a new sorted list functions for sorting lists. But by default, these in-built sorting functions will sort the list of strings in alphabetical order which would result in a wrong order in our case.

Hence, we need to pass a key argument to tell the sorting function that we need to compare the list items in a particular way and sort them accordingly. In Python, we have the datetime module which makes date based comparison easier. The datetime. It accepts two arguments: date string and format used to specify the format.

Hence, we need to pass the datetime object as the key argument in the sorting function to tell the sorting function that it needs to compare the strings by converting them into dates and sort them in the increasing order. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Writing code in comment? Please use ide. Python3 program to sort the list of dates. Function to print the data stored in the list. Sort the list in ascending order of dates. Print the dates in a sorted order.

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Check out this Author's contributed articles. Load Comments.In Python, date, time and datetime classes provides a number of function to deal with dates, times and time intervals.

Date and datetime are an object in Python, so when you manipulate them, you are actually manipulating objects and not string or timestamps. Whenever you manipulate dates or time, you need to import datetime function.

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The datetime classes in Python are categorized into main 5 classes. These import statements are pre-defined pieces of functionality in the Python library that let you manipulates dates and times, without writing any code. Consider the following points before executing the datetime code from datetime import date This line tells the Python interpreter that from the datetime module import the date class We are not writing the code for this date functionality alas just importing it for our use Step 2 Next, we create an instance of the date object.

Step 3 Next, we print the date and run the code. The output is as expected. Print Date using date. It gives date along with time in hours, minutes, seconds and milliseconds. When we execute the code for datetime, it gives the output with current date and time. Suppose we want to print just the current time without the date. We will be assigning it the current value of time using datetime. And this will give me just the time.

So let's run this program. Okay, so you can see that here I got the date and time. And then the next line, I've got just the time by itself Step 3 We will apply our weekday indexer to our weekday's arrayList to know which day is today Weekdays operator wd is assigned the number from number depending on what the current weekday is.

Here we declared the array of the list for days Mon, Tue, Wed…Sun. Use that index value to know which day it is. In our case, it is 2, and it represents Wednesday, so in the output it will print out "Which is a Wednesday. We will advance a step further and learn how to use a formatting function to format Time and Date.

Step 1 First we will see a simple step of how to format the year. It is better to understand with an example. We used the " strftime function" for formatting. This function uses different control code to give an output.

The century of the year will not display as shown in the screenshot below Step 3 Strf function can declare the date, day, month and year separately.

Also with small changes in the control code in strftime function you can format the style of the text.Not everything in the world can be ranked in alphabetical order. In Python, as in most high-level programming languages, it's very easy to sort a list of simple objects such as numbers or text strings:.

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It's when we want to sort a collection of objects that are not all the same that things get slightly more complicated:. Or, if the objects are all the same type of thing, but there's no obvious way that they should be sorted. How should a list of lists be sorted? By length of list? A real-life analogy would be trying to sort a list of movies. Sorting movie titles in alphabetical order is pretty straightforward. But how would we write a program that sorts a list of movies by quality?

It's ultimately a problem as hard as defining what "quality" means — is it number of Oscar awards? The box office receipts? The average of critics' reviews scores? But the core concept is that when we want to sort by something more ephemeral or abstract than the alphabetical order of a name, we have to do a little more work. This guide focuses on the built-in sorted function.

The Python documentation has a nice how-to tutorial that has even more ways and examples of how to do sorting. Python has a built-in function named sorted which, given an iterable collection, such as a listwill return a new list of items, but in sorted order:. Note: by " iterable collection ", I mean that sorted can deal with sequences other than lists. Strings, for example, are iterable:. By default, sorted will return numbers and text strings in ascending order, i. Of course, even that is more complicated than you might think.

python sort csv by date

Since every digital object is ultimately just a bunch of ones and zeros, letters and numbers are actually sorted by their binary values, e. Which should explain this result:. The sorted function takes a named argument, reversewhich is set to False by default.

If we want things to be sorted in reverse-order which would be descending order for character strings and numberspass True to the reverse argument:.

Besides a reverse argument, the sorted function takes one other named argument: key. However, the key argument does not take a simple value, such as True.First of all, what is a CSV? CSV Comma Separated Values is a simple file format used to store tabular data, such as a spreadsheet or database. A CSV file stores tabular data numbers and text in plain text. Each line of the file is a data record. Each record consists of one or more fields, separated by commas. The use of the comma as a field separator is the source of the name for this file format.

For working CSV files in python, there is an inbuilt module called csv. The above example uses a CSV file aapl. Run this program with the aapl. The file object is named as csvfile. The file object is converted to csv. We save the csv. Since the first row of our csv file contains the headers or field nameswe save them in a list called fields. Each row is appended to a list called rows. If you try to print each row, one can find that row is nothing but a list containing all the field values.

Writing to a CSV file. Writing a dictionary to a CSV file. Here, the file object csvfile is converted to a DictWriter object. Here, we specify the fieldnames as an argument.

So, in the end, our CSV file looks like this:. Now, while defining a csv. So, this was a brief, yet concise discussion on how to load and parse CSV files in a python program. This blog is contributed by Nikhil Kumar. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. Writing code in comment? Please use ide. What Should I Do? Web Scrapping - Legal or Illegal? How to Think Like a Programmer? This article explains how to load and parse a CSV file in Python.

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It only takes a minute to sign up. How do I optimize the for loop in this pandas script using groupby? I tried hard but I'm still banging my head against it. Using pandas.

So you can change:. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Remove duplicates from csv based on conditions Ask Question. Asked 2 years, 7 months ago.

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Active 2 years ago. Viewed 9k times. The oldest registration date among the rows must be used. DataFrame get rows for each email address and replace registration date with the oldest one this can probably be optimized using groupby for email in df['Email Address']. Ashish Acharya. Ashish Acharya Ashish Acharya 1 1 silver badge 6 6 bronze badges. Active Oldest Votes.

How to sort a Python date string list?

So you can change: for email in df['Email Address']. Now, to improve this loop: subdf['Registration Date Copy']. Since you will drop everything but the firsts elements of each group, you can change only the ones at subdf. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

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Post as a guest Name. Email Required, but never shown. The Overflow Blog. Featured on Meta. Feedback on Q2 Community Roadmap. Related 3. Hot Network Questions. Question feed.Python lists have a built-in list. There is also a sorted built-in function that builds a new sorted list from an iterable.

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A simple ascending sort is very easy: just call the sorted function. It returns a new sorted list:. You can also use the list. It modifies the list in-place and returns None to avoid confusion.

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Another difference is that the list. In contrast, the sorted function accepts any iterable. Both list. The value of the key parameter should be a function that takes a single argument and returns a key to use for sorting purposes. This technique is fast because the key function is called exactly once for each input record.

Working with csv files in Python

For example:. The key-function patterns shown above are very common, so Python provides convenience functions to make accessor functions easier and faster. The operator module has itemgetterattrgetterand a methodcaller function. The operator module functions allow multiple levels of sorting. For example, to sort by grade then by age :. This is used to flag descending sorts.

python sort csv by date

For example, to get the student data in reverse age order:. Sorts are guaranteed to be stable. That means that when multiple records have the same key, their original order is preserved. Notice how the two records for blue retain their original order so that 'blue', 1 is guaranteed to precede 'blue', 2. This wonderful property lets you build complex sorts in a series of sorting steps.

For example, to sort the student data by descending grade and then ascending agedo the age sort first and then sort again using grade :.


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