将列表转换为字符串
我已经从文件中提取了一些数据,并希望将其写入第二个文件。但我的程序返回错误:将列表转换为字符串
sequence item 1: expected string, list found
这似乎发生,因为write()
想要一个字符串,但它正在接收一个列表。
因此,关于此代码,如何将列表buffer
转换为字符串,以便我可以将buffer
的内容保存为file2
?
file = open('file1.txt','r')
file2 = open('file2.txt','w')
buffer = []
rec = file.readlines()
for line in rec :
field = line.split()
term1 = field[0]
buffer.append(term1)
term2 = field[1]
buffer.append[term2]
file2.write(buffer) # <== error
file.close()
file2.close()
尝试str.join
:
file2.write(' '.join(buffer))
文件说:
Return a string which is the concatenation of the strings in the iterable iterable. The separator between elements is the string providing this method.
如果你想把'buffer'中的每个项目写入'file2'中的一个单独的行,请使用:''\ n'.join(buffer)' – DavidRR 2015-01-20 17:01:13
@miku:这不适用于python3。 – user2284570 2015-10-20 22:55:30
@ user2284570它也可以在python3中工作。 – Dominik 2016-10-29 14:09:07
file2.write(','.join(buffer))
方法1:
import functools
file2.write(functools.reduce((lambda x,y:x+y), buffer))
方法2:
import functools, operator
file2.write(functools.reduce(operator.add, buffer))
方法3:
file2.write(''join(buffer))
在''''之后和'join'之前缺少'.'。 – ToolmakerSteve 2016-01-27 20:24:41
file2.write(str(buffer))
说明: str(anything)
将任何Python对象转换成它的字符串表示。类似于你输出的结果,如果你做print(anything)
,但是作为一个字符串。
注意:这可能不是OP想要的,因为它无法控制buffer
元素的连接方式 - 它会在每个元素之间放置,
- 但它可能对其他人有用。
buffer=['a','b','c']
obj=str(buffer)
obj[1:len(obj)-1]
会给 “ 'A', 'B', 'C'” 作为输出
# it handy if it used for output list
list = [1, 2, 3]
stringRepr = str(list)
# print(stringRepr)
# '[1, 2, 3]'
从the official Python Programming FAQ用于Python 3.6.4:
What is the most efficient way to concatenate many strings together?
str
andbytes
objects are immutable, therefore concatenating many strings together is inefficient as each concatenation creates a new object. In the general case, the total runtime cost is quadratic in the total string length.To accumulate many str objects, the recommended idiom is to place them into a list and call
str.join()
at the end:
chunks = []
for s in my_strings:
chunks.append(s)
result = ''.join(chunks)
(another reasonably efficient idiom is to use
io.StringIO
)To accumulate many bytes objects, the recommended idiom is to extend a
bytearray
object using in-place concatenation (the+=
operator):
result = bytearray()
for b in my_bytes_objects:
result += b
与该代码张贴,你应该得到oth呃错误。例如在''buffer.append [term2]''... – miku 2010-05-25 15:41:49
您似乎正在将数据添加到每行的“缓冲区”,然后将整个缓冲区写入文件而不清除它。这将导致第一行的数据在文件中的每一行都存在一次,第二行的数据少于一次,依此类推。这可能不是你想要的。 – geoffspear 2010-05-25 16:37:34