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Mastering flat_map in Python with List Comprehension

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Introduction In Python, when working with nested lists or iterables, one common challenge is flattening them into a single list while applying transformations. Many programming languages provide a built-in flatMap function, but Python does not have an explicit flat_map method. However, Python’s powerful list comprehensions offer an elegant way to achieve the same functionality. This article examines implementation behavior using Python’s list comprehensions and other methods. What is flat_map ? Functional programming  flatMap is a combination of map and flatten . It transforms the collection's element and flattens the resulting nested structure into a single sequence. For example, given a list of lists, flat_map applies a function to each sublist and returns a single flattened list. Example in a Functional Programming Language: List(List(1, 2), List(3, 4)).flatMap(x => x.map(_ * 2)) // Output: List(2, 4, 6, 8) Implementing flat_map in Python Using List Comprehension Python’...
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How to Decode TLV Quickly

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TLV format consists of three components: Tag, Length, and Value. In credit card and financial transactions, the TLV protocol utilizes this structure. Below, you will find tips for quickly decoding TLV data. 


TLV Format



According to IBM, the tag tells what type of data it is. The length field denotes the length of the value, and the value is the actual value.


Structure of TLV.


TLV comprises three field values.


  1. Tag
  2. Length
  3. Value


How to Decode TLV


The EMV labs developed tags that are part of the EMV protocol. Each tag has a unique meaning. The Tag and Length together take 1 to 4 bytes of memory.

1. The Best example for TLV.


Below is the method for decoding the EMV tag. The first part of the TLV format is TAG. The second part is LENGTH, and finally, the value.


Syntax of EMV tag:


[Tag][Value Length][Value] (ex. "9F4005F000F0A001")


where, 


Tag Name = 9F40


Value Length (in bytes) = 05 


Value (Hex representation of bytes. Example, "F0" – 1-byte) = F000F0A001


Finally, what is 9F40 tag? The EMV company assigns a value to it. Check out the complete list of EMV Tags and meanings.



2. How to read the TLV


Let me elaborate on the memory the EMV tag takes. The breakup of memory allocation is as follows.

 

Tag: 1 or 2 bytes.


Length: 05


Value length:


F0-00-F0-A0-01 ==> 5 Bytes


The F0 is the HEX value of length 1. So the total length of the value altogether is 5 bytes.


F0+00+F0+A0+01= Total 5 bytes



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