This article describes how to handle strings including line breaks [line feeds, new lines] in Python.
- Create a string containing line breaks
- Newline code
\n（LF）,\r\n（CR + LF） - Triple quote
'''or""" - With indent
- Newline code
- Concatenate a list of strings on new lines
- Split a string into a list by line breaks:
splitlines[] - Remove or replace line breaks
- Output with
print[]without a trailing newline
Create a string containing line breaks
Newline code \n（LF）, \r\n（CR + LF）
Inserting a newline code \n, \r\n into a string will result in a line break at that location.
s = 'Line1\nLine2\nLine3'
print[s]
# Line1
# Line2
# Line3
s = 'Line1\r\nLine2\r\nLine3'
print[s]
# Line1
# Line2
# Line3
On Unix, including Mac, \n [LF] is often used, and on Windows, \r\n [CR + LF] is often used as a newline code. Some text editors allow you to select a newline code.
Triple quote ''', """
You can write a string including line breaks with triple quotes ''' or """.
- Create a string in Python [single, double, triple quotes, str[]]
s = '''Line1
Line2
Line3'''
print[s]
# Line1
# Line2
# Line3
With indent
If you use triple quotes and indent, as shown below, unnecessary spaces are inserted.
s = '''
Line1
Line2
Line3
'''
print[s]
#
# Line1
# Line2
# Line3
#
By enclosing
each line in '' or "", adding a line break \n at the end, and using a backslash \, you can write as follows:
s = 'Line1\n'\
'Line2\n'\
'Line3'
print[s]
# Line1
# Line2
# Line3
It uses a mechanism in which consecutive string literals are concatenated. See the following article for details.
- Concatenate strings in Python [+ operator, join, etc.]
If you want to add indentation in the string, add a space to the string on each line.
s = 'Line1\n'\
' Line2\n'\
' Line3'
print[s]
# Line1
# Line2
# Line3
Since you can freely break lines in parentheses [], you can also write as follows using parentheses [] without using backslashes \.
s = ['Line1\n'
'Line2\n'
'Line3']
print[s]
# Line1
# Line2
# Line3
s = ['Line1\n'
' Line2\n'
' Line3']
print[s]
# Line1
# Line2
# Line3
If you just want to align the beginning of a line, you can add a backslash \ to the first line of triple quotes.
s = '''\
Line1
Line2
Line3'''
print[s]
# Line1
# Line2
# Line3
s = '''\
Line1
Line2
Line3'''
print[s]
# Line1
# Line2
# Line3
Concatenate a list of strings on new lines
You can concatenate a list of strings into a
single string with the string method, join[].
- Concatenate strings in Python [+ operator, join, etc.]
By calling join[] from a newline code \n or \r\n, each element is concatenated on new lines.
l = ['Line1', 'Line2', 'Line3']
s_n = '\n'.join[l]
print[s_n]
# Line1
# Line2
# Line3
print[repr[s_n]]
# 'Line1\nLine2\nLine3'
s_rn = '\r\n'.join[l]
print[s_rn]
# Line1
# Line2
# Line3
print[repr[s_rn]]
# 'Line1\r\nLine2\r\nLine3'
As in the example above, you can check the string with newline codes intact with the built-in function repr[].
- Built-in Functions - repr[] — Python 3.9.1rc1 documentation
Split a string into a list by line breaks: splitlines[]
You can split a string by line breaks into a list with the string method, splitlines[].
s = 'Line1\nLine2\r\nLine3'
print[s.splitlines[]]
# ['Line1', 'Line2', 'Line3']
In addition to \n and \r\n, it is also splitted by \v [line tabulation] or \f [form feed], etc.
- Built-in Types - str.splitlines[] — Python 3.9.1rc1 documentation
See also the following article for more information on splitlines[].
- Split strings in Python [delimiter, line break, regex, etc.]
Remove or replace line breaks
With splitlines[] and join[], you can remove newline codes from a string or replace them with another string.
s = 'Line1\nLine2\r\nLine3'
print[''.join[s.splitlines[]]]
# Line1Line2Line3
print[' '.join[s.splitlines[]]]
# Line1 Line2 Line3
print[','.join[s.splitlines[]]]
# Line1,Line2,Line3
It is also possible to change the newline code at once. Even if the newline code is mixed or unknown, you can split it with splitlines[] and then concatenate them with the desired code.
s_n = '\n'.join[s.splitlines[]]
print[s_n]
# Line1
# Line2
# Line3
print[repr[s_n]]
# 'Line1\nLine2\nLine3'
Since splitlines[] splits both \n [LF] and \r\n [CR + LF] as mentioned above, you don't have to worry about which newline code is used in the
string.
You can also replace the newline code replace[].
- Replace strings in Python [replace, translate, re.sub, re.subn]
s = 'Line1\nLine2\nLine3'
print[s.replace['\n', '']]
# Line1Line2Line3
print[s.replace['\n', ',']]
# Line1,Line2,Line3
However, note that it will not work if it contains a different newline code than expected.
s = 'Line1\nLine2\r\nLine3'
s_error = s.replace['\n', ',']
print[s_error]
# ,Line3Line2
print[repr[s_error]]
# 'Line1,Line2\r,Line3'
s_error = s.replace['\r\n', ',']
print[s_error]
# Line1
# Line2,Line3
print[repr[s_error]]
# 'Line1\nLine2,Line3'
You can repeat replace[] to replace multiple newline codes, but because \r\n contains \n, it doesn't work well if you
do it in the wrong order. As mentioned above, using splitlines[] and join[] is safe because you don't have to worry about line feed codes.
s = 'Line1\nLine2\r\nLine3'
print[s.replace['\r\n', ','].replace['\n', ',']]
# Line1,Line2,Line3
s_error = s.replace['\n', ','].replace['\r\n', ',']
print[s_error]
# ,Line3Line2
print[repr[s_error]]
# 'Line1,Line2\r,Line3'
print[','.join[s.splitlines[]]]
# Line1,Line2,Line3
You can use rstrip[] to remove the trailing newline code.
- Built-in Types - str.rstrip[] — Python 3.9.1rc1 documentation
s = 'aaa\n'
print[s + 'bbb']
# aaa
# bbb
print[s.rstrip[] + 'bbb']
# aaabbb
Output with print[] without a
trailing newline
By default, print[] adds a newline at the end. Therefore, if you execute print[] continuously, each output result will be displayed with a line break.
print['a']
print['b']
print['c']
# a
# b
# c
This is because the default value of the argument end of print[], which specifies the character string to be added at the end, is '\n'.
If the empty string '' is specified in end, a line break will not occur at the end.
print['a', end='']
print['b', end='']
print['c', end='']
# abc
Any string can be specified
in end.
print['a', end='-']
print['b', end='-']
print['c']
# a-b-c
However, if you want to concatenate the character strings and output, it is easier to concatenate the original character strings. See the following article.
- Concatenate strings in Python [+ operator, join, etc.]