32. Python String 转 int

在本教程中，我们将学习如何在python中将python字符串转换为int，并将int转换为String。在之前的教程中，我们了解到Python列表附加功能。

Python字符串到Int

如果您阅读了我们以前的教程，您可能会注意到我们在某些时候使用了这种转换。实际上，这在很多情况下是必要的。例如，您正在从一个文件中读取一些数据，然后它将是字符串格式，并且您必须将字符串转换为int。

现在，我们将直接进入代码。如果要将字符串中表示的数字转换为int，则必须使用int() function to do so. See the following example:

num = "123"  # string data

# print the type

print("Type of num is :", type(num))

# convert using int()

num = int(num)

# print the type again

print("Now, type of num is :", type(num))

以下代码的输出将是

Type of num is : <class "str">
Now, type of num is : <class "int">

将字符串从不同的基转换为int

如果要转换为int的字符串属于以10为底的不同基数，则可以指定转换的基数。但请记住，输出的整数总是以10为基数。你需要记住的另一件事是给定的基数必须在2到36之间。请参阅下面的示例，以了解使用基参数将字符串转换为int。

num = "123"
# print the original string
print("The original string :", num)

# considering "123" be in base 10, convert it to base 10

print("Base 10 to base 10:", int(num))

# considering "123" be in base 8, convert it to base 10

print("Base 8 to base 10 :", int(num, base=8))

# considering "123" be in base 6, convert it to base 10

print("Base 6 to base 10 :", int(num, base=6))

以下代码的输出将是

将字符串转换为int时出错

从字符串转换为int时，您可能会得到ValueError 例外. 如果要转换的字符串不代表任何数字，则会发生此异常。

假设要将十六进制数转换为整数。但你们并没有通过辩论基数=16在整数（）功能。它会引起ValueError exception if there is any digit that does not belong to the decimal number system. The following example will illustrate this exception while converting a string to int.

"""
    Scenario 1: The interpreter will not raise any exception but you get wrong data
"""
num = "12"  # this is a hexadecimal value

# the variable is considered as decimal value during conversion
print("The value is :", int(num))

# the variable is considered as hexadecimal value during conversion
print("Actual value is :", int(num, base=16))

"""
    Scenario 2: The interpreter will raise ValueError exception
"""

num = "1e"  # this is a hexadecimal value

# the variable is considered as hexadecimal value during conversion
print("Actual value of "1e" is :", int(num, base=16))

# the variable is considered as decimal value during conversion
print("The value is :", int(num))  # this will raise exception

上述代码的输出将是：

The value is : 12
Actual value is : 18
Actual value of "1e" is : 30
Traceback (most recent call last):
  File "/home/imtiaz/Desktop/str2int_exception.py", line 22, in 
    print("The value is :", int(num))  # this will raise exception
ValueError: invalid literal for int() with base 10: "1e"

Python int到String

将int转换成字符串不需要任何努力或检查。你只要用str() function to do the conversion. See the following example.

hexadecimalValue = 0x1eff

print("Type of hexadecimalValue :", type(hexadecimalValue))

hexadecimalValue = str(hexadecimalValue)

print("Type of hexadecimalValue now :", type(hexadecimalValue))

以下代码的输出将是：

Type of hexadecimalValue : <class "int">
Type of hexadecimalValue now : <class "str">

这就是Python将字符串转换为int和int到字符串转换的全部内容。

参考文献：Python官方文档