nums = [4, 9, 16, 25, -9, -100, 10000]

import math
[math.sqrt(x) for x in nums if x>=0 ]

      File "<ipython-input-7-00a6234a803b>", line 2
        [math.sqrt(x) for x in nums if x>=0 else None]
                                               ^
    SyntaxError: invalid syntax

[ math.sqrt(x)   for x in nums   ]

[2.0, 3.0, 4.0, 5.0, None, None, 100.0]

x = 100

10.0

list(reversed([1,2,3]))

[3, 2, 1]

f = open("green eggs and ham.txt")

<_io.TextIOWrapper name='green eggs and ham.txt' mode='r' encoding='cp1255'>

list(f)

['I am Sam\n',
 'I am Sam\n',
 'Sam I am\n',
 'That Sam-I-am\n',
 'That Sam-I-am!\n',
 'I do not like\n',
 'That Sam-I-am\n',
 'Do you like\n',
 'Green eggs and ham\n',
 'I do not like them\n',
 'Sam-I-am\n',
 'I do not like\n',
 'Green eggs and ham\n',
 'Would you like them\n',
 'Here or there?\n',
 'I would not like them\n',
 'Here or there\n',
 'I would not like them\n',
 'Anywhere\n',
 'I do not like\n',
 'Green eggs and ham\n',
 'I do not like them\n',
 'Sam-I-am\n',
 'Would you like them\n',
 'In a house?\n',
 'Would you like them\n',
 'With a mouse?\n',
 'I do not like them\n',
 'In a house']