A Technical I.T./DevOps Blog
Question
It seems like “global” and “nonlocal” would be the same thing. How are these keywords different in Python?
Answer
Variables inside a function are local by default; variables outside of functions are global by default. (This was taken from https://www.programiz.com/python-programming/global-keyword.) This answer/article addresses the “LEGB lexical scoping rule” (taken from page 872 of Learning Python).
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Problem Scenario
An automated process is failing. You look in the logs and they don’t help you. You have Googled the error. What should you do?
Solution
Has it ever worked? If so, did something change?
If not, Google for the command most recently entered before the error happens. New characters could be added into the command that you do not realize.
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Question
In computer programming, what is memoization?
Answer
Memoization is the act of pre-computing or pre-processing certain values for the sake of an algorithm’s performance. Rather than perform the same exact operation (which could be very complex and computationally expensive) multiple times, memoization will involve writing code to compute it once and store it in memory as a variable. This optimization can allow the call stack to have less to store (e.g.,
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Question
You want to know discretely what the third way of the three-way handshake is in the context of TCP/IP networking. What is it?
Short Answer
It is the sending of a TCP packet with a flag of “ACK” from the client to the server/destination.
Longer Answer
The third way is sending a TCP packet with the “ACK” flag (of which several potential flags are possible) to the destination:
Client —–>
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Question
You want to know discretely what the second way of the three-way handshake is in the context of TCP/IP networking. What is it?
Short Answer
It is the sending of a TCP packet with a flag of “SYN-ACK” from the server/destination to the initiating client (after the first way was completed).
Longer Answer
The second way is sending a TCP packet with the “SYN-ACK” flag (of which several potential flags are possible) to the destination:
Server —–>
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Question
You want to know discretely what the first way of the three-way handshake is in the context of TCP/IP networking. What is it?
Short Answer
It is the sending of a TCP packet with a flag of “SYN” from the client to the server/destination.
Longer Answer
TCP is used in HTTP communications. TCP uses a three-way handshake;
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Question
You are not familiar with this example of a colon. It appears to be an assignment of a value to itself. You have seen Python function signatures with colons to explain the data type. You have seen colons to signify an if conditional or a for loop. You are not sure what this line of code does:
new_var = a[i:i + counter]
What does this type of colon syntax mean?
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Problem scenario
You want to use Python to calculate the latest price of various cryptocurrencies. What should you do?
Solution
Prerequisite
This assumes you have installed pip.
Procedures
Install the Python package cryptocompare: pip install cryptocompare
Run this program:
import cryptocompare
print(cryptocompare.get_price(‘BTC’, ‘USD’))
print(cryptocompare.get_price(‘BTC’, ‘USD’))
print(cryptocompare.get_price(‘ETH’, ‘USD’))
print(cryptocompare.get_price(‘LTC’, ‘USD’))
print(cryptocompare.get_price(‘XRP’, …
Problem scenario #1
You just installed Linux on a new VM. You boot up your Debian distribution of Linux (e.g., running via Oracle VirtualBox). You see at the login prompt, “cloud-init…running modules:config…DataSourceNone…cc_final_message.py[WARNING]: Used fallback datasource”. What should you do?
Problem scenario #2
You recently created a new server. When you boot your Debian/Ubuntu/Mint server, it seems to hang with an error message about “cloud-init cc_final_message_py [warning]: used fallback datasource.” What should you do?
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