titbits from official tutorial

Question 1

how do you get print to treat inputs as raw characters

Answer 1

use r e.g. print (r ‘c:\windows\files’)

Question 2

substring extraction; in str[a:b] what is included and what is exculded?

Answer 2

a is included and b is excluded.

Question 3

name mutable objects in python

Answer 3

list, sets, dictionaries

Question 4

name some immutable objects in python

Answer 4

tuple, string, number

Question 5

simplest way to print a sequence of numbers

Answer 5

range (start, stop, step)

Question 6

by default python source code files are encoded as —-?

Answer 6

UTF8

Question 7

how to ensure a newline is NOT entered aftr the print?

Answer 7

use keyword end

Question 8

how to ensure a specific character (e.g.a comma) is entered after a print?

Answer 8

print(a, end=’,’)

Question 9

whats the difference between a set of statements enclosed by an else and followed by a for loop and a set of statements followed by a for loop (without the else)

Answer 9

If the loop has a break statement and it was exited through execution of that break as opposed to natural exhaustion of the sequence it was iterating over, then the statement in else block WILL NOT be executed whereas a block not enclosed by else WILL BE executed.

Question 10

syntax for a lambda function

Answer 10

lambda variable: expression involving variable and parameter

Question 11

what are 2 conditions under which python does not check for compiled modules

Answer 11

1. if the module is run from the python command line

2. if there is no source module, i.e, only the compiled code exists in the current directory

Question 12

what would you put in __init__.py file in a package

Answer 12

1. the list of symbols imported if import * is used.

2. any other initialization code.

Question 13

what is hr equivalent of pritnf(%d) command in python?

Answer 13

print(‘Hello {}”.format(variable_name))

Question 14

what are 2 modes in which you can open files in python?

Answer 14

text and binary mode.

Question 15

what are the two formats your data must be in to write to a file?

Answer 15

string or bytes

Question 16

what method do you use on a file object to get the curent position of the file cursor?

Answer 16

fileobject.tell()

Question 17

Moving a file pointer’ cursor to a new location is done via seek which has 2 args - one is offset, what is the other and what values can it take and what do they mean

Answer 17

“from_wat”
0- from beginning
1- fro current location
2. from end of file; now the offset has to be negative

Question 18

how do you create custom exceptions in python?

Answer 18

by deriving from the exception class

Question 19

mantra wile dealing with exceptions

Answer 19

baap can handle whatever beta can handle.

Question 20

how would you comprehend list comprehension?

Answer 20

by flatenning - unflattened:
for x in data_structure:
        for y in x
             y
[y for x in data_structure for y in x]

Question 21

Is python case sensitive?

Answer 21

yes

Question 22

what in built attribute of an object points to it’s class?

Answer 22

obj.__class__

Question 23

difference between global and non local keywords (used in front of variable names)

Answer 23

global - used to indicate that a particular variable lives in the global namespace and should be rebound there.
nonlocal - used to indicate that a particular variable lives in the enclosing namespace and must be rebound there

Question 24

what are some “Treu” quantities in Python

Answer 24

non empty string, non zero number, True, -

Question 25

pattern for reading from files

Answer 25

f = open(‘filename’, w) –> f.read() or readline() –> f.close()

Question 26

pattern of writing to files

Answer 26

f=open(“filename, w) –> f.write()

Question 27

what does // refer to?

Answer 27

floor division

Question 28

shorthand notation to `create a sequence out of string (just like slicing a string or list)

Answer 28

list[beg:end:step]

beg, beg+1step, beg+2step… untill beg+i*step

Question 29

whats the difference between append and extend for lists

Answer 29

a = [1,2,3] b =[5,6]

a. append(b); now a willbe [1,2,3, [5,6]]
a. extend(b); now a will be [1,2,3,5,6]

Question 30

list.insert(index,object), what is the value of list[index]

Answer 30

object

Question 31

what 4 files does pypi need in order to work

Answer 31

setup.py, setup.cfg, LICENSE.txt, README.md

Question 32

what command do you run to upload your package to pip python

Answer 32

python setup.py register sdist upload
regsiter name on pypi
sdist - create a source distribution in the name of the tarfile in the top level of your source code
upload -command to uplaod.

Question 33

how to call the base class constructor from the derived class

Answer 33

super(derived_class, self).__init__(value=20)