Python regex for integer

Question

I m learning regex and I would like to use a regular expression in Python to define only integers - whole numbers but not decimals   I could make one that only allows numbers by using  d  but it also allows decimal numbers  which I don t want   price   TextField    Price          validators Regexp   d   message    This is not an integer number  please see the example and try again         validators Optional        How can I change the code to only allow integers

User · Answer

You are apparently using Django   You are probably better off just using models IntegerField   instead of models TextField    Not only will it do the check for you  but it will give you the error message translated in several langs  and it will cast the value from it s type in the database to the type in your Python code transparently

User · Answer

Regexp work on the character base  and  d means a single digit 0   9 and not a decimal number   A regular expression that matches only integers with a sign could be for example    -    0-9      meaning     - start of string  -    - an optional  this is what   means  minus or plus sign  0-9   - one or more digits  the plus means  one or more  and  0-9  is another way to say  d    - end of string   Note  having the sign considered part of the number is ok only if you need to parse just the number  For more general parsers handling expressions it s better to leave the sign out of the number  source streams like 3-2 could otherwise end up being parsed as a sequence of two integers instead of an integer  an operator and another integer  My experience is that negative numbers are better handled by constant folding of the unary negation operator at an higher level

User · Answer

You need to anchor the regex at the start and end of the string     0-9      Explanation            Start of string  0-9     one or more digits 0-9          End of string

User · Answer

I prefer   -     1-9  d  0   because   -    0-9    allows the string starting with 0   RE INT   re compile r   -     1-9  d  0       class TestRE unittest TestCase       def test int self           self assertFalse RE INT match               self assertFalse RE INT match  -             self assertTrue RE INT match  1            self assertTrue RE INT match   1            self assertTrue RE INT match  -1            self assertTrue RE INT match  0            self assertTrue RE INT match   0            self assertTrue RE INT match  -0             self assertTrue RE INT match  11            self assertFalse RE INT match  00            self assertFalse RE INT match  01            self assertTrue RE INT match   11            self assertFalse RE INT match   00            self assertFalse RE INT match   01            self assertTrue RE INT match  -11            self assertFalse RE INT match  -00            self assertFalse RE INT match  -01             self assertTrue RE INT match  1234567890            self assertTrue RE INT match   1234567890            self assertTrue RE INT match  -1234567890

[python] Python regex for integer?

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