Pandas exercise 1

>>>>import pandas as pd
>>>df = pd.DataFrame({"val": list(zip(range(9), range(9)[::-1]))})

>>>df 

use query to subset the df using the first entry(>3) of the tuple. 

      val
0  (0, 8)
1  (1, 7)
2  (2, 6)
3  (3, 5)
4  (4, 4)
5  (5, 3)
6  (6, 2)
7  (7, 1)
8  (8, 0)
Solution:
#Access the first elements of the tuple
>>> df.val.str[0]
0    0
1    1
2    2
3    3
4    4
5    5
6    6
7    7
8    8
>>> df.val.str[0].to_frame().query('val > 3')
   val
4    4
5    5
6    6
7    7
8    8
.str will work with any object column (this includes columns of lists and tuples), not just strings (strings are considered objects, one of many possible types).

list exercise in python

1. Write a Python program to sum all the items in a list
2. Write a Python program to multiplies all the items in a list

   >>>l
   [4, 5, 6, 7]
   >>> reduce(lambda x,y:x*y,l)
   840

3. Write a Python program to get the largest number from a list
4. Write a Python program to get the smallest number from a list
5. Write a Python program to find the list of words that are longer than n from a given list of words.
6. Write a Python program to count the number of strings where the string length is 2 or more and the first and last character are same from a given list of strings.

   >>> s=['12341','aaa','abc', 'xyz', 'aba', '1221','xx']
   >>> new_s=[x for x in s if len(x)>=2 and x[0]==x[-1]]
   >>> new_s
   ['12341', 'aaa', 'aba', '1221', 'xx']

7. Write a Python program to get a list, sorted in increasing order by the last element in each tuple from a given list of non-empty tuples.
8.  Sample List : [(2, 5), (1, 2), (4, 4), (2, 3), (2, 1)]
   Expected Result : [(2, 1), (1, 2), (2, 3), (4, 4), (2, 5)]
   >>> l= [(2, 5), (1, 2), (4, 4), (2, 3), (2, 1)]
   >>>l.sort(key=lambda x:x[1])
   >>>l
   [(2, 1), (1, 2), (2, 3), (4, 4), (2, 5)]
   [or]
   >>> import operator
   >>> l= [(2, 5), (1, 2), (4, 4), (2, 3), (2, 1)]
   >>> l.sort(key=operator.itemgetter(1))
   >>> l
   [(2, 1), (1, 2), (2, 3), (4, 4), (2, 5)]
9. Write a Python program to remove duplicates from a list
10. Write a Python program to check a list is empty or not
11.  Write a Python program to remove all the elements from a list(empty the list).
12. Write a proram to remove all occurences of a element(ex:5) from a list.
    >>> l=[2,3,4,2,3,4,5,6,7,5,4,2]
    >>> filter(lambda x:x!=5,l)
    [2, 3, 4, 2, 3, 4, 6, 7, 4, 2]
13.  Write a Python program to clone or copy a list.
14. Write a Python function that takes two lists and returns True if they have at least one common member.
15. Write a Python program to print a specified list after removing the 0th, 4th and 5th elements.
    Sample List : ['Red', 'Green', 'White', 'Black', 'Pink', 'Yellow','Red']
    Expected Output : ['Green', 'White', 'Black','Red']
    >>> slist=['Red', 'Green', 'White', 'Black', 'Pink', 'Yellow','Red']
    >>> nlist=[e for i,e in enumerate(slist) if i not in [0,4,5]]
    >>> nlist
    ['Green', 'White', 'Black', 'Red']
    
16. Write a Python program to generate a 3*4*6 3D array, whose each element is *
17. Write a Python program to print the numbers of a specified list after removing even numbers from it
18. Write a Python program to shuffle and print a specified list
    >>> l=[1,2,3,4,5,6,3,4,8,9,22,44,54,31,23]
    >>> random.shuffle(l)
    >>> l
    [23, 44, 4, 1, 5, 4, 54, 9, 22, 31, 6, 2, 3, 8, 3]
    
19.  Write a Python program to generate and print a list of first and last 5 elements where the values are square of numbers between 1 and 30 (both included).
    >>> l=list(range(31))
    >>> l=[x*x for x in l[1:6]+l[-5:]]
    >>> l
    [1, 4, 9, 16, 25, 676, 729, 784, 841, 900]
20. Write a Python program to generate and print a list except for the first 5 elements, where the values are square of numbers between 1 and 30 (both included).
    >>> l=list(range(31))
    >>> l=[x*x for x in l[5:-5]]
21. Write a Python program to generate all permutations of a list in Python.
    >>> import itertools
    >>> l=[1,2,3,4]
    >>> list(itertools.permutations(l,2))
    [(1, 2), (1, 3), (1, 4), (2, 1), (2, 3), (2, 4), (3, 1), (3, 2), (3, 4), (4, 1), (4, 2), (4, 3)]
22. Write a Python program to get the difference between the two lists
    >>> x=[1,2,3]
    >>> y=[4,5,6]
    >>> list(set(x)^set(y))
    [or]
    >>> list(set(x).symmetric_difference(y))
    [1, 2, 3, 4, 5, 6]
23. Write a Python program access the index of a list. 
24. Write a Python program to convert a list of characters into a string.
25. Write a Python program to find the index of an item in a specified list.
26. Write a Python program to flatten a shallow list.
    >>> l=[[1,2,3],[4,5],[7,8,9]]
    >>> from itertools import chain
    >>> list(chain(*l))
    [1, 2, 3, 4, 5, 7, 8, 9]
    [or]
    >>> l=[[1,2,3],[4,5],[7,8,9]]
    >>> sum(l,[])
    [1, 2, 3, 4, 5, 7, 8, 9]
27. Write a Python program to append a list to the second list.
28. Write a Python program to select an item randomly from a list.
    >>> l=list(range(31))
    >>> random.choice(l)
    13
29. Write a python program to check whether two lists are circularly identical.
30. Write a Python program to get unique values from a list.
    >>> l=[1,2,3,4,5,3,4,8]
    >>> list(set(l))
    [1, 2, 3, 4, 5, 8]
31. Write a Python program to find the second smallest number in a list.
32. Write a Python program to find the second largest number in a list.
33. Write a Python program to get the frequency of the elements in a list
    >>> l=[1,2,3,4,5,3,4,8]
    >>> {x:l.count(x) for x in l}
    {1: 1, 2: 1, 3: 2, 4: 2, 5: 1, 8: 1}
34. Write a Python program to count the number of elements in a list within a specified range.
    >>> x=[10,23,21,45,65,34,25,78,54,43,89]
    >>> len([i for i in x if i>=30 and i<=60])
    4
35. Write a Python program to check whether a list contains a sublist.
36. Write a Python program to generate all sublists of a list