Python Overview

From MantidProject

Python Basics

• Variable assignment in Python is simpler than in other languages as you do not specify types

# Here x is initialized to 5 and Python then treats this as an integer
x = 5
# It can be incremented and have all of the expected operations applied to it
x += 1

# Later on it can be used for something else
x = "a string"  # Now x is a string and adding a number produces an error
x + 5
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'int' objects

• To convert objects to a string use the str() function

x = 42
"The answer is " + str(x)

• Note that, in this case, str(x) is not the same as 'x'

• The Python for loop is much the same as in other languages

for i in range(0, 5):
    print i

# Prints numbers 0 -> 4

# Lists can be accessed directly
fibs = [1,1,2,3,5]
for i in fibs:
    print i

# prints each value in the list

• Testing values is also similar

if x < 5:
    print "Do something for lower regime"
elif x == 5:
    print "Do something for match"
else:
    print "Do something for upper regime"

• Most importantly, Python uses indentation not braces to mark whether you are still within a function, if-statement or for loop.

previous contents next