python input() 没有按预期工作
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python input() not working as expected
提问by liv2hak
I am a python newbie.I am getting familiar with loops and tried this example from a book
我是 python 新手。我熟悉循环并从书中尝试过这个例子
while True:
s = input('Enter something : ')
if s == 'quit':
break
print('Length of the string is', len(s))
print('Done')
However the output is as follows
但是输出如下
Enter something : ljsdf
Traceback (most recent call last):
File "trial_2.py", line 2, in <module>
s = input('Enter something : ')
File "<string>", line 1, in <module>
NameError: name 'ljsdf' is not defined
采纳答案by Christian
You have to use raw_input()instead (Python 2.x), because input()is equivalent to eval(raw_input()), so it parses and evaluates your input as a valid Python expression.
您必须raw_input()改用 (Python 2.x)，因为input()等效于eval(raw_input())，因此它会将您的输入解析并评估为有效的 Python 表达式。
while True:
s = raw_input('Enter something : ')
if s == 'quit':
break
print('Length of the string is', len(s))
print('Done')
Note:
笔记：
input()doesn't catch user errors (e.g. if user inputs some invalid Python expression). raw_input()can do this, because it converts the input to a string. For futher information, read Python docs.
input()不捕捉用户错误（例如，如果用户输入了一些无效的 Python 表达式）。raw_input()可以这样做，因为它将输入转换为string. 如需更多信息，请阅读 Python 文档。
回答by mhlester
you want raw_input()in python2
你想raw_input()在python2中
while True:
s = raw_input('Enter something : ')
if s == 'quit':
break
print 'Length of the string is', len(s)
print 'Done'
input()tries to evaluate (dangerously!) what you give it
input()试图评估（危险的！）你给它的东西
回答by falsetru
It seems like you're using Python 2.x, while the code is expected to be run in Python 3.x.
看起来您使用的是 Python 2.x，而代码预计将在 Python 3.x 中运行。
inputin Python 2.xevaluates the input string unlike inputin Python 3.x.
input在 Python 2.x 中评估输入字符串与inputPython 3.x不同。
回答by Vipul
Your code will work fine in python 3.x
您的代码将在 python 3.x 中正常工作
But if you are using python 2 you will have to input string using raw_input()
但是，如果您使用的是 python 2，则必须使用 raw_input() 输入字符串
while True: s = raw_input('Enter something : ') if s == 'quit': break print('Length of the string is', len(s)) print('Done')
while True: s = raw_input('Enter something : ') if s == 'quit': break print('Length of the string is', len(s)) print('Done')
回答by linzwatt
In Python 2.x input()is designed to return numbers, int or float depending on the input from the user, you can also enter variable names.
在 Python 2.xinput()中，根据用户的输入返回数字、整数或浮点数，您还可以输入变量名。
you need to use:
你需要使用：
raw_input('Enter something: ')
The error is caused because Python thinks that "ljsdf" is the name of a variable, and that's why it raises this exception:
错误是因为 Python 认为 "ljsdf" 是变量的名称，这就是它引发此异常的原因：
NameError: name 'ljsdf' is not defined
NameError: name 'ljsdf' is not defined
becuase "ljsdf" is not defined as a variable. :D
因为“ljsdf”未定义为变量。:D
raw_input()is safer to use, and then convert the input to whatever other type after :D
raw_input()使用更安全，然后在 :D 之后将输入转换为任何其他类型
