Python 输出字符串的前 100 个字符
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/3486384/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Output first 100 characters in a string
提问by Blankman
Can seem to find a substring function in python.
似乎可以在 python 中找到一个子字符串函数。
Say I want to output the first 100 characters in a string, how can I do this?
假设我想输出字符串中的前 100 个字符，我该怎么做？
I want to do it safely also, meaing if the string is 50 characters it shouldn't fail.
我也想安全地做到这一点，意思是如果字符串是 50 个字符，它就不应该失败。
采纳答案by icktoofay
print my_string[0:100]
回答by Arkady
Easy:
简单：
print mystring[:100]
回答by czchen
From python tutorial:
来自python 教程：
Degenerate slice indices are handled gracefully: an index that is too large is replaced by the string size, an upper bound smaller than the lower bound returns an empty string.
退化切片索引被优雅地处理：太大的索引被替换为字符串 size，小于下限的上限返回一个空字符串。
So it is safe to use x[:100].
所以使用起来是安全的x[:100]。
回答by paxdiablo
Slicing of arrays is done with [first:last+1].
数组的切片是用[first:last+1].
One trick I tend to use a lot of is to indicate extra information with ellipses. So, if your field is one hundred characters, I would use:
我经常使用的一个技巧是用省略号表示额外的信息。因此，如果您的字段是一百个字符，我会使用：
if len(s) <= 100:
print s
else:
print "%s..."%(s[:97])
And yes, I know ()is superfluous in this case for the %formatting operator, it's just my style.
是的，我知道()在这种情况下对于%格式化操作符来说是多余的，这只是我的风格。
回答by John La Rooy
To answer Philipp's concern ( in the comments ), slicing works ok for unicode strings too
为了回答 Philipp 的担忧（在评论中），切片也适用于 unicode 字符串
>>> greek=u"αβγδεζηθικλμνξοπρ?στυφχψω"
>>> print len(greek)
25
>>> print greek[:10]
αβγδεζηθικ
If you want to run the above code as a script, put this line at the top
如果要将上面的代码作为脚本运行，请将此行放在顶部
# -*- coding: utf-8 -*-
If your editor doesn't save in utf-8, substitute the correct encoding
如果您的编辑器没有以 utf-8 格式保存，请替换正确的编码
回答by Julien Kieffer
Most of previous examples will raise an exception in case your string is not long enough.
如果您的字符串不够长，前面的大多数示例都会引发异常。
Another approach is to use
'yourstring'.ljust(100)[:100].strip().
另一种方法是使用
'yourstring'.ljust(100)[:100].strip().
This will give you first 100 chars. You might get a shorter string in case your string last chars are spaces.
这将为您提供前 100 个字符。如果您的字符串最后一个字符是空格，您可能会得到一个较短的字符串。
回答by OrangeSherbet
String formatting using %is a great way to handle this. Here are some examples.
使用字符串格式化%是处理这个问题的好方法。这里有些例子。
The formatting code '%s'converts '12345'to a string, but it's already a string.
格式化代码'%s'转换'12345'为字符串，但它已经是字符串。
>>> '%s' % '12345'
'12345'
'%.3s'specifies to use only the first three characters.
'%.3s'指定仅使用前三个字符。
>>> '%.3s' % '12345'
'123'
'%.7s'says to use the first seven characters, but there are only five. No problem.
'%.7s'说使用前七个字符，但只有五个。没问题。
>>> '%.7s' % '12345'
'12345'
'%7s'uses up to seven characters, filling missing characters with spaces on the left.
'%7s'最多使用七个字符，用左边的空格填充缺失的字符。
>>> '%7s' % '12345'
' 12345'
'%-7s'is the same thing, except filling missing characters on the right.
'%-7s'是一样的，除了在右边填充缺失的字符。
>>> '%-7s' % '12345'
'12345 '
'%5.3'says use the first three characters, but fill it with spaces on the left to total five characters.
'%5.3'说使用前三个字符，但用左边的空格填充它总共五个字符。
>>> '%5.3s' % '12345'
' 123'
Same thing except filling on the right.
除了在右边填充之外，同样的事情。
>>> '%-5.3s' % '12345'
'123 '
Can handle multiple arguments too!
也可以处理多个参数！
>>> 'do u no %-4.3sda%3.2s wae' % ('12345', 6789)
'do u no 123 da 67 wae'
If you require even more flexibility, str.format()is available too. Here is documentationfor both.
回答by Szymek G
[start:stop:step]
So If you want to take only 100 first character, use your_string[0:100]or your_string[:100]If you want to take only the character at even position, use your_string[::2]The "default values" for start is 0, for stop - len of string, and for step - 1. So when you don't provide one of its and put ':', it'll use it default value.
因此，如果您只想取 100 个第一个字符，请使用your_string[0:100]或your_string[:100]如果您只想取偶数位置的字符，请使用your_string[::2]start 的“默认值”为 0，停止 - 字符串的 len，以及步骤 - 1。所以当您不提供其中之一并放置“：”时，它将使用它的默认值。
