Difference between revisions of "Python-lists"

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parsing lists in python
 
parsing lists in python
  
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===Example #1 (some basic list manipulation)===
 
===Example #1 (some basic list manipulation)===

Latest revision as of 13:40, 23 December 2020

parsing lists in python


(back to python-datastructures)

Example #1 (some basic list manipulation)

#
#
# python list examples
#
# #1 one-dimensional ('flat/unnested') lists


list1 = [1,2,3.14,'red','green'] 


# NOTE#1: strings may be surrounded by apostrophes or quotes or mixed
#         the output will convert quotes to apostrophes
#
#goodlist = [1,2,3.14,'red','green']  # strings with apostrophes
#goodlist = [1,2,3.14,'red',"green"]  # mixed apostrophes and quotes
#goodlist = [1,2,3.14,"red","green"]  # all quotes

# NOTE#2: don't surround lists with quotes or apostrophes!
#
#wronglist = '[1,2,3.14,"red","green"]' # list surrounded by apostrophes
#wronglist = "[1,2,3.14,'red','green']" # list surrounded by quotes

print('list1: ' + str(list1) )

# NOTE#3: concatenate a list to a string by surrounding it with 'str()'
#
# print('list1: ' + list1)      # incorrect
# print('list1: ' , list1)      # ok, but shows parenthesis and quotes from string
# print('list1: ' + str(list1)) # correct
# print(list1)                  # correct (but not concatenated)

for x in list1:
    print(x)

print('')
print('')



print ('show 4th element: ' + str(list1[3]))

print('')

print('modify 4th element from \'red\' to \'blue\'')

list1[3] = 'blue'

print('')

print ('show 4th element: ' + str(list1[3]))

print('')
print('')




print('add new element \'orange\' at the end:')

list1.append('orange')

print('')

print('list1: ' + str(list1))

print('')
print('')


print('insert new element \'17\'at the beginning:')

list1.insert(0,17)

print('')

print('list1: ' + str(list1))

print('')
print('')



print('delete element with name \'green\':')

list1.remove('green')

print('')

print('list1: ' + str(list1))

print('')
print('')


# NOTE#4: if a list contains multiple elements with the same value then 'remove' only removes the first matching element


print('delete the third element:')

list1.pop(2)

print('')

print('list1: ' + str(list1))

print('')
print('')


# NOTE#5: use 'pop()' to delete the last element


Example #2 (nested lists)

#
#
# python list examples
#
# #2 - nested lists


list2 = ['joe', 186, ['swimming', 'running'], [1983,2001,2018], 5, 2] 


print('list2: ' + str(list2) )

for x in list2:
    print(x)

print('')
print('')



print('iterate over the third element (index 2)')

for x in list2[2]:
    print(x)

print('')
print('')


print('show the length of the list')
print('list2: ' + str(list2) )
print('length: ' + str(len(list2)) + '   (counting nested lists as 1)' )

print('')
print('')




print('show which elements are lists:')
for x in list2:

    if isinstance(x, list):
        print(str(x) + ' is a list')
    else:
        print(str(x) + ' is not a list')

print('')
print('')



print('list2: ' + str(list2) )
print('add the element \'walking\' to the list at index 2:')
list2[2].append('walking')
print('list2: ' + str(list2) )

print('')
print('')




print('list2: ' + str(list2) )
print('remove the first element from the list at index 3:')
list2[3].pop(0)
print('list2: ' + str(list2) )

print('')
print('')


Example #3 (bigger nested list)

#
#
# python list examples
#
# #3 - bigger nested list


list3 = [[110.3, 111.5,110.1, 110.2],[110.2,112.7,109.4,111.6],[111.6,109.3,110.8,111.5]]

print('list3: ' + str(list3) )
print('')


print('print each nested list:')
for x in list3:
    print(x)

print('')
print('')



print('only show the second and third element of each nested list')
for x in list3:

    print(x[1], x[2])

print('')
print('')



print('print the index position and the first element of each nested list')
for (i,x) in enumerate(list3):

    print(i, x[0])

print('')
print('')


Example #4 (list containing a dictionary)

#
#
# python list examples
#
# #4 - list containing a dictionary


list4 = [{'symbol': 'ETHBTC', 'price': '0.03014900'}, {'symbol': 'LTCBTC', 'price': '0.00413500'}]
print('list4: ' + str(list4) )
print('')


print('print each nested dictionary:')
for x in list4:
    print(x)

print('')
print('')

 
# NOTE: below is an example of parsing a dictionary, which is not a list.
#       See examples for dictionaries for more details
#
print('iterate through each dictionary')
for x in list4:

    marketname = x['symbol']
    price = x['price']

    print('market name: ' + str(marketname))
    print('price: ' + str(price))
    print('')

print('')
print('')