Преобразование списка строк в список целых чисел в Python
В этом посте мы обсудим, как преобразовать список строк в список целых чисел в Python.
Например, список [«1», «2», «3», «4», «5»] следует преобразовать в список [1, 2, 3, 4, 5] .
1. Использование map() функция
Рекомендуемое решение — вызвать встроенную функцию map() для эффективного преобразования списка строк в список целых чисел. Он применяет указанную функцию к каждому элементу списка, получая результаты. Поскольку он возвращает итератор, преобразуйте результат в список. Эта функция показана ниже:
Как преобразовать массив в число python
Interconversion between data types is facilitated by python libraries quite easily. But the problem of converting the entire list of strings to integers is quite common in the development domain. Let’s discuss a few ways to solve this particular problem.
Method 1: Using eval()
Python eval() function parse the expression argument and evaluate it as a python expression and runs Python expression(code), If the expression is an int representation, Python converts the argument to an integer.
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Output:
Method 2: Naive Method
This is the most generic method that strikes any programmer while performing this kind of operation. Just looping over the whole list and converting each string of the list to int by type casting.
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Output:
Method 3: Using list comprehension
This is just a kind of replica of the above method, just implemented using list comprehension, a kind of shorthand that a developer looks for always. It saves the time and complexity of coding a solution.
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Output:
Method 4: Using map()
This is the most elegant, pythonic, and recommended method to perform this particular task. This function is exclusively made for this kind of task and should be used to perform them.
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Output:
Method 5: List of strings with mixed integer representations
Here, we will first convert each string to a float first and then we will convert it into an integer by using the round() function, otherwise, it will through error.
Convert list of ints to one number?
I have a list of integers that I would like to convert to one number like:
What is the best way to implement the magic function?
EDIT
I did find this, but it seems like there has to be a better way.
19 Answers 19
The map -oriented solution actually comes out ahead on my box — you definitely should not use sum for things that might be large numbers:
Just for completeness, here’s a variant that uses print() (works on Python 2.6-3.x):
Time performance of different solutions
I’ve measured performance of @cdleary’s functions. The results are slightly different.
Each function tested with the input list generated by:
You may supply your own function via —sequence-creator=yourmodule.yourfunction command-line argument (see below).
The fastest functions for a given number of integers in a list ( len(nums) == digit_count ) are:
len(nums) in 1..30
len(nums) in 30..1000
To plot the first figure download cdleary.py and make-figures.py and run ( numpy and matplotlib must be installed to plot):
A one-liner without needing to cast to and from str
This method works in 2.x as long as each element in the list is only a single digit. But you shouldn’t actually use this. It’s horrible.
Using a generator expression:
if the list contains only integer:
This seems pretty clean, to me.
I found some examples are not compatible with python 3 I test one from @Triptych
s = filter(str.isdigit, repr(numList)) num = int(s)
in python 3 it’s gonna give error
TypeError: int() argument must be a string, a bytes-like object or a number, not ‘filter’
i think the more simple and compatible way would be
This may be helpful
If you happen to be using numpy (with import numpy as np ):
I think this seems to be the simplest solution with no need for any fcn
NOTE: This implementation is in Python 3
I found this thread while trying to convert a list to the real value of the underlying int in terms of a C-style pointer, but none of the other answers appear to work for this case. I think the following solution works as intended and could be useful to others even though it doesn’t necessarily answer the original question.
How to convert a float array to an integer array in python ?
Examples of how to convert a float array to an integer array in python:
Table of contents
Using the numpy function astype
To convert a float array to an integer array in python, a solution is to use astype, example:
Round the numbers before converting them in integer
It is also possible to round the numbers and after convert them to integer using the numpy function around
Note: work also with the function rint, example
Truncate the numbers first
Round to the nearest bigger integer
Round to the nearest smaller integer
References
| Links | Site |
|---|---|
| astype | docs.scipy.org |
| around | scipy doc |
| rint | doc scipy |
| trunc | doc scipy |
| ceil | doc scipy |
| floor | doc scipy |
| How to convert 2D float numpy array to 2D int numpy array? | stackoverflow |
| Rounding | scipy doc |
| Better rounding in Python’s NumPy.around: Rounding NumPy Arrays | stackoverflow |
| are numpy array elements rounded automatically? | stackoverflow |
Author 
Benjamin
Greetings, I am Ben! I completed my PhD in Atmospheric Science from the University of Lille, France. Subsequently, for 12 years I was employed at NASA as a Research Scientist focusing on Earth remote sensing. Presently, I work with NOAA concentrating on satellite-based Active Fire detection. Python, Machine Learning and Open Science are special areas of interest to me.