在python中将numpy、list或float转换为字符串
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Convert numpy, list or float to string in python
提问by jw21
I'm writing a python function to append data to text file, as shown in the following,
我正在编写一个python函数来将数据附加到文本文件中，如下所示，
The problem is the variable, var, could be a 1D numpy array, a 1D list, or just a float number, I know how to convert numpy.array/list/floatto string separately (meaning given the type), but is there a method to convert varto string without knowing its type?
问题是可变的，var，可能是一维numpy的阵列，一维列表，或者只是一个浮点数，我知道如何转换numpy.array/ list/float串单独（给定类型的意思），但有一种方法来转换var为字符串不知道它的类型？
def append_txt(filename, var):
my_str = _____ # convert var to string
with open(filename,'a') as f:
f.write(my_str + '\n')
Edit 1: Thanks for the comments, sorry maybe my question was not clear enough.
str(var)on numpy would give something like []. For example, var = np.ones((1,3)), str(var)will give [[1. 1. 1.]], and []is unwanted,
编辑 1：感谢您的评论，抱歉，也许我的问题不够清楚。
str(var)在 numpy 上会给出类似[]. 例如，var = np.ones((1,3)), str(var)会给[[1. 1. 1.]]，并且[]是不需要的，
Edit 2: Since I want to write clean numbers (meaning no [or ]), it seems type checking is inevitable.
编辑 2：由于我想写干净的数字（意思是 no[或]），似乎类型检查是不可避免的。
回答by rajeshv90
If you don't know what is the type of var you can check type using
如果您不知道 var 的类型是什么，则可以使用检查类型
from collections import Iterable
if isinstance(var,Iteratable):
mystring=''.join(map(str,var))
else:
mystring=str(var)
回答by DavidK
回答by Sudip Kafle
stris able to convert any type into string. It can be numpy.array / list / float
str能够将任何类型转换为字符串。它可以是 numpy.array/list/float
# using numpy array
new_array = numpy.array([1,2,3])
str(new_array)
>> '[1 2 3]'
# using list
new_list = [1, 2, 3]
str(new_list)
>> '[1, 2, 3]'
# using float
new_float = 1.1
str(new_float)
>> '1.1'
回答by Banana
Type checking is not the only option to do what you want, but definitely one of the easiest:
类型检查不是做你想做的事情的唯一选择，但绝对是最简单的选择之一：
import numpy as np
def to_str(var):
if type(var) is list:
return str(var)[1:-1] # list
if type(var) is np.ndarray:
try:
return str(list(var[0]))[1:-1] # numpy 1D array
except TypeError:
return str(list(var))[1:-1] # numpy sequence
return str(var) # everything else
EDIT:Another easy way, which does not use type checking(thanks to jtaylor for giving me that idea), is to convert everything into the same type (np.array) and then convert it to a string:
编辑：另一种不使用类型检查的简单方法（感谢 jtaylor 给我这个想法）是将所有内容转换为相同类型 ( np.array)，然后将其转换为字符串：
import numpy as np
def to_str(var):
return str(list(np.reshape(np.asarray(var), (1, np.size(var)))[0]))[1:-1]
Example use(both methods give same results):
示例使用（两种方法给出相同的结果）：
>>> to_str(1.) #float
'1.0'
>>> to_str([1., 1., 1.]) #list
'1.0, 1.0, 1.0'
>>> to_str(np.ones((1,3))) #np.array
'1.0, 1.0, 1.0'
