CODEWITHSUNDEEP
pythonexception
Joschua
Joschua

Reputation: 6034

Python 3: Why does splitlines() on a str results in TypeError? (but not always)

Maybe I'm just too tired to see it, but why does this

cmds = '''
AA ''' + ''' BB
'''.splitlines()

result in

Traceback (most recent call last):
  File "<pyshell#15>", line 3, in <module>
    '''.splitlines()
TypeError: Can't convert 'list' object to str implicitly

and this works just fine:

cmds = '''
AA ''' + ''' BB
'''
print(cmds.splitlines())

?

Upvotes: 1

Views: 899

Answers (3)

Holloway
Holloway

Reputation: 7377

You first example is splitting the second string before trying to join it to the first string. The second example is joining the two strings first, then splitting it.

Upvotes: 0

davidlowryduda
davidlowryduda

Reputation: 2559

It is the order in which operations are done. In

cmds = '''
AA ''' + ''' BB
'''.splitlines()

the splitlines() successfully splits the second string

''' BB
'''

but then it tries to concatenate the result (a list) to the first string

'''
AA '''

which doesn't make sense. In the second snippet, the concatenations happens first, and then splitlines works just fine.

Upvotes: 0

schesis
schesis

Reputation: 59158

The splitlines method is getting called before the addition, so this:

cmds = '''
AA ''' + ''' BB
'''.splitlines()

... is equivalent to this:

cmds = ('''
AA ''') + (''' BB
'''.splitlines())

... which means you're trying to add a list to a string.

However, in the second case:

cmds = '''
AA ''' + ''' BB
'''
print(cmds.splitlines())

... you're doing the addition first, and calling splitlines on the result.

Upvotes: 3

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