Hi,
say I have the following list:
myList = [['john', '1', '2:00pm'], ['becky', '2', '3:15pm'], ['tom', '3', '3:20pm']]
the type of every elements in the inner list is string. How do I change (or what is the pythonic way) to change
the type of the 2nd element in the inner list to integer and the 3rd element to date.time?
Thank you!
I tried the following codes but didn't get the result that I wanted.
myList_chg = [int(x[1]) for x in myList]
>>>myList_chg
Output:
[1, 2, 3]
myList_chg_2 = [myList[0], int(x[1]) for x in myList, myList[2]]
Error:
SyntaxError: invalid syntax
I wanted to access the 2nd elements of the inner list using the following code but it retrieved the following instead:
>>> myList[:][0]
Output:
['john', '1', '2:00pm']
>>> for i in myList:
... print i[1]
...
1
2
3
>>>
import sys
myList = [['john', '1', '2:00pm'], ['becky', '2', '3:15pm'], ['tom', '3', '3:20pm']]
def get_myList_item(row=0, column=0):
try:
# Python 3.6.0
print(f'row: {row}, column: {column} contains {myList[row][column]}')
# other python:
print('row: {}, column: {} contains {}'.format(row, column, myList[row][column]))
except:
print("Unexpected exception:", sys.exc_info()[0])
if __name__ == '__main__':
get_myList_item(row=1,column=0)result:
Output:
row: 1, column: 0 contains becky
Here a hint for integer convert.
>>> my_list = [['john', '1', '2:00pm'], ['becky', '2', '3:15pm'], ['tom', '3', '3:20pm']]
>>> [[int(x) for x in lst] for lst in my_list]
Error:
Traceback (most recent call last):
File "<string>", line 301, in runcode
File "<interactive input>", line 1, in <module>
File "<interactive input>", line 1, in <listcomp>
File "<interactive input>", line 1, in <listcomp>
ValueError: invalid literal for int() with base 10: 'john
Now it try to convert all element in the nested list.
Can wirte a helper function that catch
ValueError
def try_int(x):
try:
return int(x)
except ValueError:
return x
Now try again:
>>> [[try_int(x) for x in lst] for lst in my_list]
[['john', 1, '2:00pm'], ['becky', 2, '3:15pm'], ['tom', 3, '3:20pm']]
Quote:3rd element to date.time?
Do you know how to this,like with only 1 value
'3:20pm'?
Apologies, I tried to reply to this last night but my internet was having issues.
Here's something close to what you want
newList = [(name, int(num), f(time)) for (name, num, time) in myList]
where f() is whatever conversion you want for time.
I believe this is preferable over mutating things in-place, as a general habit, but if memory is a concern, you could write a loop over myList in which for each sublist, you use indexes to replace the values with their relative modifications.