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What is the difference between tuples and lists in Python?

+1 vote
What is the difference between tuples and lists in Python?
posted Sep 15, 2017 by Jdk

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1 Answer

+1 vote

List is similar to arrays in C but it can have items of different datatypes. Difference between list and tuple is that, Lists are enclosed in brackets ( [ ] ) and their elements and size can be changed, while tuples are enclosed in parentheses ( ( ) ) and cannot be updated.

answer Sep 27, 2017 by Afzal Labeeb
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+4 votes

I have a list of tuples where the number of rows in the list and the number of columns in tuples of the list will not be constant. i.e.

list = [(a1,b1, …z1), (a2,b2, …, z2),…. ,(am,bm, … , zm )]. It can be compared to the SQL results, as the number of columns change in the sql, the number of columns change in the list of tuples as well.

I have to iterate through each element of each tuple in the list, perform some checks on the value, convert it and return the modified values as a new list of tuples.

i.e.  list_value = [(‘name1’, 1234, ‘address1’ ), (‘name2’, 5678, ‘address2’), (‘name3’, 1011, ‘addre”ss3’)] 

I need to access each value to check if the value contains a double quote and enclose the string containing double quote with double quotes. The transformation should return

list_value = [(‘name1’, 1234, ‘address1’ ), (‘name2’, 5678, ‘address2’), (‘name3’, 1011, ‘”addre”ss3”’)] 

The simplest approach for me would be to do this:

mod_val = [transform(row) for row in list_value] 
def transform(row): 
   while index < len(row): 
...    if isinstance(row[index],basestring): 
...       if " in row[index]: 
...          mod_list.append("+row[index]+") 
...    else: 
...       mod_list.append(row[index]) 
...    index = index+1 
... return mod_list 

Is there a way to make the code concise using list comprehension?

+1 vote

I want to find the maximal number of elements contained in a nested dictionary, e.g.

data = {
 'col1': {'err': [elem1, elem2, elem3]},
 'col2': {'err': [elem1, elem2]}

so to find the maximal number of elements in the lists for key 'err' in key 'col1' and 'col2'. Also key 'violations' may contain many keys (e.g. 'col1' , 'col2', 'col3' etc), so what's the best way to do this (using a loop)?

max = 0for col in data.violations:
 if max < len(data.violations.col.err):
 max = len(data.violations.col.err)
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