how to write a correct python code

1a = [3, 4, 5]
2a = [i + 3]
3

1$ pycodestyle optparse.py
2optparse.py:69:11: E401 multiple imports on one line
3optparse.py:77:1: E302 expected 2 blank lines, found 1
4optparse.py:88:5: E301 expected 1 blank line, found 0
5optparse.py:222:34: W602 deprecated form of raising exception
6optparse.py:347:31: E211 whitespace before '('
7optparse.py:357:17: E201 whitespace after '{'
8optparse.py:472:29: E221 multiple spaces before operator
9optparse.py:544:21: W601 .has_key() is deprecated, use 'in'
10

1my_very_big_string = (
2    "For a long time I used to go to bed early. Sometimes, "
3    "when I had put out my candle, my eyes would close so quickly "
4    "that I had not even time to say “I’m going to sleep.”"
5)
6
7from some.deep.module.inside.a.module import (
8    a_nice_function, another_nice_function, yet_another_nice_function)
9

1d = {'hello': 'world'}
2
3print(d.get('hello', 'default_value')) # prints 'world'
4print(d.get('thingy', 'default_value')) # prints 'default_value'
5
6# Or:
7if 'hello' in d:
8    print(d['hello'])
9

1# Another possible scenario# You got a reward amount from somewhere else, but don't know if None/0 or notreward = reward_known or "500 dollars"# The above line of code is equivalent to belowreward = reward_known if reward_known else "500 dollars"

1four_lists = [[] for __ in range(4)]
2

1a = [3, 4, 5]
2b = a
3
4# assign the variable "a" to a new list without changing "b"
5a = [i + 3 for i in a]
6