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ii:labs:02:tasks:01 [2021/11/07 15:04] radu.mantu |
ii:labs:02:tasks:01 [2024/10/25 01:48] (current) radu.mantu |
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| - | ==== 01. [30p] Intro, datatypes and more ==== | + | ==== 01. [25p] Intro, datatypes and more ==== |
| Up until now, you should have had some interaction with the //C language// (or even, with //C++//). Normally, you would write your code in a source file, compile it with **gcc** and most likely get a few dozen errors. Eventually, you would end up with a binary executable file (i.e.: an [[https://refspecs.linuxfoundation.org/elf/elf.pdf|ELF]]). | Up until now, you should have had some interaction with the //C language// (or even, with //C++//). Normally, you would write your code in a source file, compile it with **gcc** and most likely get a few dozen errors. Eventually, you would end up with a binary executable file (i.e.: an [[https://refspecs.linuxfoundation.org/elf/elf.pdf|ELF]]). | ||
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| </code> | </code> | ||
| - | Notice how we we accessed the real and imaginary parts of the complex number ''c''? Being able to do this should immediately remind of structures in //C//, or classes in //C++//. We should investigate this further... | + | Notice how we accessed the real and imaginary parts of the complex number ''c''? Being able to do this should immediately remind of structures in //C//, or classes in //C++//. We should investigate this further... |
| <code python> | <code python> | ||
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| So the //complex// type has two internal variables that hold the real and imaginary parts of the number. But what's this? It also has a method (i.e.: function) defined. Try to invoke **conjugate()** for ''c''. Does it work? Does it change the **imag** and **real** internal variables? | So the //complex// type has two internal variables that hold the real and imaginary parts of the number. But what's this? It also has a method (i.e.: function) defined. Try to invoke **conjugate()** for ''c''. Does it work? Does it change the **imag** and **real** internal variables? | ||
| - | Well, that was an interesting detour. But let's get back to our numbers. As you might imagine, all the basic arithmetic operators work in python pretty much like they would in //C//; even the modulus operator. There are, however, two extra ones that might be useful: //exponentiation// and //floor division//: | + | Well, that was an interesting detour. But let's get back to our numbers. As you might imagine, all the basic arithmetic operators work in //Python// pretty much like they would in //C//; even the modulus operator. There are, however, two extra ones that might be useful: //exponentiation// and //floor division//: |
| <code python> | <code python> | ||
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| ... "and his comrades would chuckle at the sheer treason of it." | ... "and his comrades would chuckle at the sheer treason of it." | ||
| - | >>> the length of the string can be obtained using len() | + | >>> # the length of the string can be obtained using len() |
| >>> len(s) | >>> len(s) | ||
| 230 | 230 | ||
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| # here, we extract every second month starting with January | # here, we extract every second month starting with January | ||
| - | # the z in [x:y:z] is basically the iteration step | + | # the z in [x:y:z] is the iteration step |
| # in this case, x and y didn't need to be explicitly stated | # in this case, x and y didn't need to be explicitly stated | ||
| >>> months[0:12:2] | >>> months[0:12:2] | ||
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| ['January', 'March', 'May', 'July', 'September', 'November'] | ['January', 'March', 'May', 'July', 'September', 'November'] | ||
| - | # here, we extract months ranging from the one indexed 6th to the one indexed 0th, in reverse order | + | # here, we extract months ranging from the one indexed 6th to the one indexed 0th (excluding it), in reverse order |
| >>> months[6:0:-1] | >>> months[6:0:-1] | ||
| + | ['July', 'June', 'May', 'April', 'March', 'February'] | ||
| </code> | </code> | ||
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| </code> | </code> | ||
| - | Let's take a closer look at the final two examples. In the first, we used the //Python// equivalent of the //C// ternary operator: ''it %%**%% 3 if it % 2 == 0 else None''. This would roughly translate to ''(it % 2 == 0) ? pow(it, 3) : None''. Notice that in this example, we either have to have ''it ** 3'' or ''None''. In other words, we can't drop the ''else''. Otherwise, we would get an invalid syntax error. For a similar outcome however, we have the second example. Here, the use of ''if it % 2 == 1'' at the end is specific to this type of array initialization and will most likely generate an error in any other contexts. | + | Let's take a closer look at the final two examples. In the first, we used the //Python// equivalent of the //C// ternary operator: ''it %%**%% 3 if it % 2 == 0 else None''. This would roughly translate to ''(it % 2 == 0) ? pow(it, 3) : None''. Notice that in this example, we either have to have ''it ** 3'' or ''None''. In other words, we can't drop the ''else''. Otherwise, we would get an invalid syntax error. For a similar outcome however, we have the second example. Here, the use of ''if it % 2 == 1'' at the end is specific to this type of array initialization and will most likely generate an error in any other context. |
| Since we know how to initialize an array, and access elements of an array, all that's left is manipulating an array. | Since we know how to initialize an array, and access elements of an array, all that's left is manipulating an array. | ||
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| >>> list(t) | >>> list(t) | ||
| ['pi', 3.1415, True] | ['pi', 3.1415, True] | ||
| - | >>> list(t) + [ '3', .5772, True ] | + | >>> list(t) + [ 'e', 2.7182, True ] |
| - | ['pi', 3.1415, True, '3', 0.5772, True] | + | ['pi', 3.1415, True, 'e', 2.7182, True] |
| >>> # similarly, a tuple can be generated from a list | >>> # similarly, a tuple can be generated from a list | ||
| - | >>> tuple(list(t) + [ '3', .5772, True ]) | + | >>> tuple(list(t) + [ 'e', 2.7182, True ]) |
| - | ('pi', 3.1415, True, '3', 0.5772, True) | + | ('pi', 3.1415, True, 'e', 2.7182, True) |
| >>> # tuples can be used as a shortcut to assign multiple values at once | >>> # tuples can be used as a shortcut to assign multiple values at once | ||
