Python extend method for lists decompose elements of the first list in to the second
Apparently, I have a problem with my code. I run the below module with Python 3.6.6 Shell. I want to check whether elements of size 4 exists on list a_list and copy them to b_list. There is only one such element ('3m7n'), but it is decomposed in 4 others ('3', 'm', '7', 'n'). Why?
a_list = ['2', '3m7n', '3', '17', None]
b_list = ['bat', 'zoo', 'next', 'pina', 'pinta']
for i in a_list:
if i==None:
pass
elif len(i)==4:
b_list.extend(i)
b_list
['bat', 'zoo', 'next', 'pina', 'pinta', '3', 'm', '7', 'n']
enter image description here
python loops
asked Nov 26 '18 at 3:57
RamonRamon
156
add a comment |
Apparently, I have a problem with my code. I run the below module with Python 3.6.6 Shell. I want to check whether elements of size 4 exists on list a_list and copy them to b_list. There is only one such element ('3m7n'), but it is decomposed in 4 others ('3', 'm', '7', 'n'). Why?
a_list = ['2', '3m7n', '3', '17', None]
b_list = ['bat', 'zoo', 'next', 'pina', 'pinta']
for i in a_list:
if i==None:
pass
elif len(i)==4:
b_list.extend(i)
b_list
['bat', 'zoo', 'next', 'pina', 'pinta', '3', 'm', '7', 'n']
enter image description here
python loops
asked Nov 26 '18 at 3:57
RamonRamon
156
Can you please paste the code as text in your question? It is hard people to help with an image of your code.
– slider
Nov 26 '18 at 4:00
Useappendinstead ofextend. stackoverflow.com/questions/252703/…
– slider
Nov 26 '18 at 4:04
add a comment |
Apparently, I have a problem with my code. I run the below module with Python 3.6.6 Shell. I want to check whether elements of size 4 exists on list a_list and copy them to b_list. There is only one such element ('3m7n'), but it is decomposed in 4 others ('3', 'm', '7', 'n'). Why?
a_list = ['2', '3m7n', '3', '17', None]
b_list = ['bat', 'zoo', 'next', 'pina', 'pinta']
for i in a_list:
if i==None:
pass
elif len(i)==4:
b_list.extend(i)
b_list
['bat', 'zoo', 'next', 'pina', 'pinta', '3', 'm', '7', 'n']
enter image description here
python loops
asked Nov 26 '18 at 3:57
RamonRamon
156
Apparently, I have a problem with my code. I run the below module with Python 3.6.6 Shell. I want to check whether elements of size 4 exists on list a_list and copy them to b_list. There is only one such element ('3m7n'), but it is decomposed in 4 others ('3', 'm', '7', 'n'). Why?
a_list = ['2', '3m7n', '3', '17', None]
b_list = ['bat', 'zoo', 'next', 'pina', 'pinta']
for i in a_list:
if i==None:
pass
elif len(i)==4:
b_list.extend(i)
b_list
['bat', 'zoo', 'next', 'pina', 'pinta', '3', 'm', '7', 'n']
enter image description here
python loops
python loops
asked Nov 26 '18 at 3:57
RamonRamon
156
asked Nov 26 '18 at 3:57
RamonRamon
156
edited Nov 27 '18 at 16:23
Ramon
asked Nov 26 '18 at 3:57
RamonRamon
156
asked Nov 26 '18 at 3:57
RamonRamon
156
asked Nov 26 '18 at 3:57
RamonRamon
156
156
Can you please paste the code as text in your question? It is hard people to help with an image of your code.
– slider
Nov 26 '18 at 4:00
Useappendinstead ofextend. stackoverflow.com/questions/252703/…
– slider
Nov 26 '18 at 4:04
add a comment |
Can you please paste the code as text in your question? It is hard people to help with an image of your code.
– slider
Nov 26 '18 at 4:00
Useappendinstead ofextend. stackoverflow.com/questions/252703/…
– slider
Nov 26 '18 at 4:04
Can you please paste the code as text in your question? It is hard people to help with an image of your code.
– slider
Nov 26 '18 at 4:00
Can you please paste the code as text in your question? It is hard people to help with an image of your code.
– slider
Nov 26 '18 at 4:00
Use
append instead of extend. stackoverflow.com/questions/252703/…– slider
Nov 26 '18 at 4:04
Use
append instead of extend. stackoverflow.com/questions/252703/…– slider
Nov 26 '18 at 4:04
add a comment |
2 Answers
2
active
oldest
votes
extend expects a list
append expects an element
a_list = ['2', '3m7n', '3', '17']
b_list = ['bat', 'zoo', 'next']
b_list.extend([i for i in a_list if len(i) == 4 ])
print(b_list)
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
add a comment |
append adds an object to the end of the list, as a list is a mutable data type, you can append to the end of a list. extend adds each element in an iterable to the end of the list.
The mistake you are making is extending a list with a str sequence, if you want to add an object use append:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.append(i)
b
['bat', 'zoo', 'next', '3', 'm', '7', 'n']
The error you made using extend is where you extended the list with a string, which then treats it as an iterable and goes through each character of the string, similar to something like for i in '3m7n': print(i). Using the same context, but converting each item in the loop to a list, you use extend to add each item in the list:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.extend([i])
b
>>['bat', 'zoo', 'next', '3m7n']
For the sake of simplicity, readability and a little more efficiency, you can use a list comprehension to replace the for loop:
b.extend([i for i in a if len(i) == 4 ])
And if you observe, it works exactly the same as the for loop, by extending the list with a list object.
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
extend expects a list
append expects an element
a_list = ['2', '3m7n', '3', '17']
b_list = ['bat', 'zoo', 'next']
b_list.extend([i for i in a_list if len(i) == 4 ])
print(b_list)
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
add a comment |
extend expects a list
append expects an element
a_list = ['2', '3m7n', '3', '17']
b_list = ['bat', 'zoo', 'next']
b_list.extend([i for i in a_list if len(i) == 4 ])
print(b_list)
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
add a comment |
extend expects a list
append expects an element
a_list = ['2', '3m7n', '3', '17']
b_list = ['bat', 'zoo', 'next']
b_list.extend([i for i in a_list if len(i) == 4 ])
print(b_list)
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
extend expects a list
append expects an element
a_list = ['2', '3m7n', '3', '17']
b_list = ['bat', 'zoo', 'next']
b_list.extend([i for i in a_list if len(i) == 4 ])
print(b_list)
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
answered Nov 26 '18 at 4:06
KrishnaKrishna
6021515
6021515
add a comment |
add a comment |
append adds an object to the end of the list, as a list is a mutable data type, you can append to the end of a list. extend adds each element in an iterable to the end of the list.
The mistake you are making is extending a list with a str sequence, if you want to add an object use append:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.append(i)
b
['bat', 'zoo', 'next', '3', 'm', '7', 'n']
The error you made using extend is where you extended the list with a string, which then treats it as an iterable and goes through each character of the string, similar to something like for i in '3m7n': print(i). Using the same context, but converting each item in the loop to a list, you use extend to add each item in the list:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.extend([i])
b
>>['bat', 'zoo', 'next', '3m7n']
For the sake of simplicity, readability and a little more efficiency, you can use a list comprehension to replace the for loop:
b.extend([i for i in a if len(i) == 4 ])
And if you observe, it works exactly the same as the for loop, by extending the list with a list object.
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
add a comment |
append adds an object to the end of the list, as a list is a mutable data type, you can append to the end of a list. extend adds each element in an iterable to the end of the list.
The mistake you are making is extending a list with a str sequence, if you want to add an object use append:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.append(i)
b
['bat', 'zoo', 'next', '3', 'm', '7', 'n']
The error you made using extend is where you extended the list with a string, which then treats it as an iterable and goes through each character of the string, similar to something like for i in '3m7n': print(i). Using the same context, but converting each item in the loop to a list, you use extend to add each item in the list:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.extend([i])
b
>>['bat', 'zoo', 'next', '3m7n']
For the sake of simplicity, readability and a little more efficiency, you can use a list comprehension to replace the for loop:
b.extend([i for i in a if len(i) == 4 ])
And if you observe, it works exactly the same as the for loop, by extending the list with a list object.
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
add a comment |
append adds an object to the end of the list, as a list is a mutable data type, you can append to the end of a list. extend adds each element in an iterable to the end of the list.
The mistake you are making is extending a list with a str sequence, if you want to add an object use append:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.append(i)
b
['bat', 'zoo', 'next', '3', 'm', '7', 'n']
The error you made using extend is where you extended the list with a string, which then treats it as an iterable and goes through each character of the string, similar to something like for i in '3m7n': print(i). Using the same context, but converting each item in the loop to a list, you use extend to add each item in the list:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.extend([i])
b
>>['bat', 'zoo', 'next', '3m7n']
For the sake of simplicity, readability and a little more efficiency, you can use a list comprehension to replace the for loop:
b.extend([i for i in a if len(i) == 4 ])
And if you observe, it works exactly the same as the for loop, by extending the list with a list object.
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
append adds an object to the end of the list, as a list is a mutable data type, you can append to the end of a list. extend adds each element in an iterable to the end of the list.
The mistake you are making is extending a list with a str sequence, if you want to add an object use append:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.append(i)
b
['bat', 'zoo', 'next', '3', 'm', '7', 'n']
The error you made using extend is where you extended the list with a string, which then treats it as an iterable and goes through each character of the string, similar to something like for i in '3m7n': print(i). Using the same context, but converting each item in the loop to a list, you use extend to add each item in the list:
a = ['2', '3m7n', '3', '17']
b = ['bat', 'zoo', 'next']
for i in a:
if len(i) == 4:
b.extend([i])
b
>>['bat', 'zoo', 'next', '3m7n']
For the sake of simplicity, readability and a little more efficiency, you can use a list comprehension to replace the for loop:
b.extend([i for i in a if len(i) == 4 ])
And if you observe, it works exactly the same as the for loop, by extending the list with a list object.
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
answered Nov 26 '18 at 5:21
BernardLBernardL
2,40811130
2,40811130
add a comment |
add a comment |
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Can you please paste the code as text in your question? It is hard people to help with an image of your code.
– slider
Nov 26 '18 at 4:00
Use
appendinstead ofextend. stackoverflow.com/questions/252703/…– slider
Nov 26 '18 at 4:04