Python for syntax conversion

[kingsman]

(a) I am ten years old
I love eating apple
I am a boy

(b) Apple is my favourite fruit
I am a male
I have birthed 10 years

Here is a basic algorithmic scheme that you could follow for such a work

Output:
Description of the input language: it has 3 statements

    age_stm:
        syntax: "I am <number> years old"
        parameters:
            number: a number written in english

    eating_stm:
        syntax: "I love eating <food>"
        parameters:
            food: the name of some food

    gender_stm:
        syntax: "I am a <gender>"
        parameters:
            gender: boy or girl

First step: PARSING OF THE INPUT FILE

    The aim of this step is to recognize the statements contained
    in the input file and their parameters. In the example, the result is
    a sequence of python objects

    age_stm(number = ten)
    eating_stm(food = apple)
    gender_stm(gender = boy)

Second step: CODE GENERATION

    each parsed statement is translated in a statement of the second
    language according to a specific rule

    rule for an age_stm:
        convert the number in english to a number in digits
        emit the statement "I have birthed <digits> years"

    rule for a eating_stm:
        identify the type of the food (eg apple is a fruit)
        emit the statement "<food> is my favorite <food type>"

    rule for a gender_stm:
        convert the gender to the appropriate transcription (boy -> male)
        emit the statement "I am a <converted gender>"

There may be many more rules, for example there may be rules to change the
order of the emited statements, also a single input statement may induce
more than one output statement, etc.

These are the codes I have create

File = open('First.txt', 'r')
thing = []
for line in File:
    thing.append(line)
first_stm = thing[0]
second_stm = thing[1]
third_stm = thing[2]
number = (first_stm.split()[2])
food = (second_stm.split()[3])
gender = (third_stm.split()[3])
File.close()


Conversion = open('First conversion', 'w+')
Conversion.write(food + ' is my favourite fruit\n')
if gender == 'boy':
    Conversion.write('I am a male')
else:
    Conversion.write('I am a female')
Conversion.close()

For the first statement, I need to convert ten to 10.
But there are various situations, the age can be 11, 13 ,46, 57, 65
So, how can I convert it from a string to digit.
For the third statement, the case is just boy or girl, It does not similar to the first statement that having so many options.

---

How about imitate the third statement using 'if' statement
for example

if number == 'one'
Conversion.write('I have birthed 1 years')
elif number == 'two'
Conversion.write('I have birthed 2 years')

If I use this method, I need to use 'if' for many time such as 100 time to satisfy the reality case(100 years old)
Is there any easier method to deal with it?