In Python program to get the the input from user we will use input() method. In python 2x we used raw_input() method. So when we show input prompt the current program execution will stop until user enter the value. When reading the value from the command line using input(), the resulting value is a string even we enter digits also it treats as String.
Example to take inputs from user
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def main():
print("Enter your Name")
name = input('Your name: ')
print('Hello ' + name + ', how are you?')
main()
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When we run it will prompt user to enter the values
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Enter your Name |
Let's say if we Add numbers entered by the user
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def main():
a = input('First number: ')
b = input('Second number: ')
print(a + b)
main()
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Now when we run the program and enter numbers as
First number: 1
Second number: 2
It will add this two digits as string and give the output as 12 instead of 3, why because we already said every input value treat as string in python, so how we will convert these string values to numbers and add two numbers.
To fix the issue of adding two numbers from python user input prompt, we should have to convert string to numbers.
Let's write example add two numbers in Python
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def main():
a = input('First number: ')
b = input('Second number: ')
print(int(a) + int(b))
main()
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This will output like below
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First number: 1 Second number: 2 3 |
So to convert string to number we can use int(),float() functions in python
How can i check the given string can be converted to number in python?
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def main():
val = input("Type in a number: ")
print(val)
print(val.isdecimal())
print(val.isnumeric())
if val.isdecimal():
num = int(val)
print(num)
main()
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output
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Type in a number: 12 |
So in the above example to check the given string is converted to number or not by isdecimal() or isnumaric() functions
Converting String to int
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def main():
a = "12"
print(a)
print( type(a) )
b = int(a)
print(b)
print( type(b) )
a = "Age 18 is Major"
print(a)
print( type(a) )
b = int(a)
print(b)
print( type(b) )
main()
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Output
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12 |
Simple Calculator with python
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def main():
a = float(input("Number: "))
b = float(input("Number: "))
op = input("Operator (+-*/): ")
if op == '+':
res = a+b
elif op == '-':
res = a-b
elif op == '*':
res = a*b
elif op == '/':
res = a/b
else:
print("Invalid operator: '{}'".format(op))
return
print(res)
return
main()
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How to read Command line arguments in Python
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import sys;
def main():
print(sys.argv)
print(sys.argv[0])
print(sys.argv[1])
print(sys.argv[2])
main()
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run in terminal by
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D:\pythonexamples>example.py 1 2 3 4 1 2 3 |
To find length of the command line arguments by len(sys.argv) method
Conclusion: In this python tutorial we covered how to take input from user and convert input string to numbers, python type conversion
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