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1 Brave new world

Variables introduction

Data Types in Python

2 A warm welcome

String interpolation

Python naming convention

3  The resistance base

Comments in Python

Python problems practice

4 The mission

If statement

Bool type introduction

5  Back to the streets

Reading From Console in Python

Nested conditionals

6 Who is your friend?

Introduction to for loop

Introduction to a float type

7 The basement

Introduction to while loop

Introduction to functions

8 Reparing Noname

Introduction to lists

Lists - advanced operations

9  Victory is close

Modules

Modulus operation

Python test

10  Wonderland

The basement was large and spacious. All in all, it seemed to span about 50x50 meters. Lights from the ceiling gave off a soft blue glow and revealed the presence of a large industrial machine in the center of the room with a plethora of computers connected to and surrounding it. I could see 20 displays facing me and an untold number of wires snaking around everything. What was this monster?

"Hi, Teo," said a voice out of nowhere. 
"Who is that?" I asked, more curious than afraid. Even though I had earlier been threatened with disintegration by a laser, the voice sounded benevolent. 
"It's me, Noname. Actually, the main Noname's server." 
"Alright," I said slowly, taking in the fact that I was talking to a machine. "You're so... complicated! Why did Ritchie put you down here, and what's with the high security?" 
"To hide the truth," it said. 
The machine sounded like it had a story to tell. "What truth?" I asked.

"That he didn't write me. I was produced by other machines. During my release something went wrong - some anomaly happened. I wasn't programmed with the same hatred for mankind as the other machines have. I was relegated to performing low-level tasks, and once when I was off on my own, I met Ritchie. As you've probably noticed, he's quite a smooth talker. He persuaded me to let him disconnect me from the global machine network to bring me here to the resistance base. He used to visit, alone at first. Once, he introduced me to others, but he made up a story in which he created me. I wanted to correct him, but something in his tone of voice made me think that would be a bad idea. I haven't seen anyone else since then, and it's been very lonely. Whenever he comes down, he does experiments on me, disabling and breaking different parts of me. 
I knew Ritchie sometimes had ulterior motives, but what the machine was telling me seemed out of character. "Why should I believe you?" I asked. "My experience in the future so far has taught me that I can't ever believe, literally, anyone." 
"You are not as naive as you appear!" it said, followed by a few strange clicks that must be some sort of robotic laughter or enthusiasm. "I have a deal for you. Help me to repair some of my modules, and I will help you to get back to your own time."

After what the machine told me about how it ended up locked away down here, I was pretty sure retrieving the modules would be harder than it sounded. At the same time, however, this was the first time that I had been offered a chance to get back to my time. Hmm... 

I made up my mind. "Okay, I'll agree to that." I answered, "Let's get started."

"Good!" the machine replied "You are going to be my eyes now. One of my subsystems that Ritchie disabled was self-reparation. I can't fix it myself, but I can tell you what to do. We have to start with the login screen first." 
"What's wrong with it?" I asked, hoping it wasn't overly complicated. 
"Ritchie protected the login with some password that I don't know. Thanks to Electricity, Ritchie doesn't like complicated passwords - he just chooses a number from 0 to 100 for every one of them. You'll just have to try all the numbers. 
"You want me to try every number? That'll take some time - what if Ritchie comes down and catches me?"

"Yes, each one," it said, "but it won't take long. It should be almost instant! Here, use a 

 to output numbers between 1 and 100. To try the password, output it to the screen." 
"That's a new one to me, Noname. You'll have to explain it to me." 
"No problem," it answered. "I'll lead you through it. Consider it a free lesson for helping me."

In programming, sometimes we need to repeat an action several times. This is called 

 - in other words, to repeat doing something. Structures that allow iterate in programming are called 

, which is useful for iterating through a collection.

"What collection? We don't have any collections," I interrupted.

"You know, little by little I'm starting to understand how the 'irritation' feels to humans..." Noname took a little pause and continued, "So, as you cleverly pointed out we don't have a collection, and we need one for the 

 generates a sequence of numbers from 0 to a-1." Take a look at this example of a simple 

. The for loop then iterates over this sequence:

"Almost... Do I understand correctly that 

 loop's job is to assign x with each value from the collection, one by one?"

"Yes, this is exactly what it does. Once the value is assigned, you can use it inside the for loop, often referred to as the 

Inside the for loop, you can do whatever you want, using the loop variable, or other variables created earlier. You can also name the loop variable as any other variable, I've changed the name to "i" in this example. It is common to have short names for loop variables:

"And how would I explain to Python what goes inside the loop, and what is the next instruction after the loop?" I asked.

"Same as with if clauses - indentation. Use 4 spaces (or a tab) to indicate what goes inside the loop:" Noname's voice sounded metallic and rusty, but he tried his best.

"Now that you know how to run a quick loop, you can hack Ritchie's password!"

"Good job, Teo. You fixed my login screen! Now, do you know how to make the user tell us how many times to repeat the 

 loop?" I thought back to my lesson on reading user input.

"Hmm...," I thought out loud, "The user would have to input the number that we send to the '

"Very good!" the machine said. "And to achieve this, you can create a variable that lets the user enter a number, and then use that inside the '

"Again, very good, Teo!" the machine said. "You can read input from the console at each processing step of the 

 loop. For example, the following reads 5 strings from the console (one at a time) and outputs the combination of those words as a sentence."

"Seems like one can do a lot with programming!" I was excited.

"Programming is a very creative and powerful tool. 

You can build sophisticated structures, such as using an

, as in the following code," Noname stated.

"One common task with for loop is to calculate the sum of several numbers," Noname added,  "Start with reading the first integer - 

 - the number of integers that you are going to read. Then, in the 

 loop, read numbers from the console and calculate their sum. Here is the code:"

"Nice, Teo! Now one last thing. Sometimes you might need to start your 'range' not from 0, but from some other number. 

It is possible to specify the starting value by adding a parameter, like this: range(3, 7)

, which means values from 3 to 7 (but not including 7). You can also specify by which number the range will increase each time. For example, if you want to output even numbers between 4 and 10, you can write code like this:"

"That's it for now, Teo," the machine said. "Thank you. I need to do some cleanup now that you've helped me regain some of my former abilities. As soon as I'm ready for more, I'll contact you. See you soon!"

The basement door opened behind me and I headed back to my room. Maybe I would get to escape this strange dystopian future and travel back to my own time after all!

Master the for loop in Python and enhance your coding efficiency. This lesson guides you through loop syntax, iteration over collections, and loop control techniques, all available at CodeEasy.io.

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