How to convert string to int type

In programming, we often encounter situations where we need to convert a string (str) into an integer (int). This may be because we need to perform numerical calculations on strings, or need to convert user-entered strings into integers for processing. This article will show you how to convert a string to an integer.

1. Use the built-in function int()

Python provides a built-in function int() that can be used to convert strings to integers. The basic syntax of this function is as follows:

int(string, base)

Among them, string is the string to be converted, and base is an optional parameter, indicating the base of the string. If the base is not specified, the default is decimal.

To convert a string to an integer, just use the int() function passing the string as a parameter. An example is as follows:

num_str = "123" # 定义一个字符串
num_int = int(num_str) # 将字符串转换为整数
print(num_int) # 输出：123
print(type(num_int)) # 输出：

2. Use try-except to handle exceptions

When converting a string into an integer, you may encounter some problems. For example, the string contains non-numeric characters, or the value represented by the string exceeds the range of integers. To prevent the program from crashing during conversion, we can use try-except statements to handle exceptions.

When using the int() function to convert a string, if an exception occurs, Python will raise a ValueError exception. Therefore, we can use try-except to catch this exception and handle it accordingly.

num_str = "abc" # 包含非数字字符的字符串
try:
num_int = int(num_str)
print(num_int)
except ValueError:
print("字符串不能转换为整数")

In the above example, since the string contains the non-numeric character "abc", the int() function cannot convert it to an integer, so a ValueError exception is raised. In the except block, we output a corresponding prompt message.

3. Use regular expressions

Another way to convert a string to an integer is to use a regular expression. Regular expressions are a powerful pattern matching tool that can be used to extract specific patterns from strings.

We can use the findall() function in the re module to find the numeric pattern in the string and extract it. We can then use the int() function to convert the extracted list of strings into integers.

import re
num_str = "I have 123 apples" # 包含数字的字符串
numbers = re.findall(r'\d+', num_str) # 使用正则表达式查找数字模式
int_list = [int(num) for num in numbers] # 将字符串列表转换为整数列表
print(int_list) # 输出：[123]

In the above example, the regular expression r'\d ' means matching one or more numeric characters. The findall() function returns a list of all matching strings. We then use list comprehensions to convert these strings into integers.

Summary:

This article introduces three methods of converting strings to integers. Using the int() function is the most common method, but you need to pay attention to handling exceptions. Use regular expressions to extract numeric patterns in strings and convert them to integers. In practical applications, choose the most appropriate method to convert strings to integers according to the specific situation. .

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