Convert string to int value python

Question

I want to convert a string to a specific int value in Python i.e. "red" I want to be 1, "blue" to 2, etc. I am currently using if-else statements. I have a dataset of strings with common strings that I want to associate with a number. Please help.

def discretize_class(x):
 if x == 'first':
 return int(1)
 elif x == 'second':
 return int(2)
 elif x == 'third':
 return int(3)
 elif x == 'crew':
 return int(4)

• Vishnu Upadhyay: Please show what you have tried?
• Ffisegydd: Please add your code to do the question, not in a comment.
• Vincent Beltman: Use a dictionary d = {'first': 1, 'second': 2}. Than you can say d['first'] which will retun 1
• user3318660: how would I convert a dataset of strings to a dictionary?

Answer 1

You need to use a dictionary. That would be best I think:

dictionary = {'red': 1, 'blue': 2}
print dictionary['red']

Or with the new code you added just now:

def discretize_class(x):
 dictionary = {'first': 1, 'second': 2, 'third': 3, 'crew': 4}
 return dictionary[x]
print discretize_class('second')

Answer 2

Assuming, by datasets, you either mean a

• text file
• database table
• a list of strings

So first thing importantly, you need to know, how you can read the data. Example for

• test file: You can simply read the file and iterate through the file object
• database table: Based on what library you use, it would provide an API to read all the data into a list of string
• list of strings: Well you already got it

Enumerate all the strings using the built-in enumerate

Swap the enumeration with the string

Either use dict-comprehension (if your python version supports), or convert the list of tuples to a dictionary via the built-in `dict

with open("dataset") as fin:
 mapping = {value: num for num, value in enumerate(fin)}

This will provide a dictionary, where each string, ex, red or blue is mapped to a unique number

• user3318660: so i have a dataset where the first line is "third, adult, male, yes" second line is "second, adult, female, yes", etc. I want third to equal the same int value throughout,and so on.

Answer 3

Your question is a bit vague, but maybe this helps.

common_strings = ["red","blue","darkorange"]
c = {}
a = 0
for item in common_strings:
 a += 1 
 c[item] = a
# now you have a dict with a common string each with it's own number.