Python Guide: From Zero to Hero Part 1

Introduction

 

This is a detailed tutorial designed for coders who need to learn the Python programming language from scratch. In this course, I will try to highlight many of Python's capabilities and features. Python is an easy-to-learn programming language.

 

 

Your First Program

>>> print "Hello World"
Hello World
>>>

On UNIX:

#!/usr/local/bin/python

print "Hello World"

Expressions

 

Expressions are the same as with other languages as in the following:

Variables

 

Variables are not tied to a memory location like in C. They are dynamically typed.

a = 4 << 3

b = a * 4.5

if-else

# find the maximum (z) of a and b

if a < b:
   z = b

else:
    z = a

elif statement

 

PS: There is no “switch” statement.

if a == ’+’:
 op = PLUS

elif a == ’-’:
 op = MINUS

elif a == ’*’:
 op = MULTIPLY

else:
 op = UNKNOWN

The while statement

while a < b:
# Do something
 a = a * 2

The for statement

for i in [3, 4, 10, 25]:
     print i

Tuples:

Tuples are like lists, but the size is fixed at the time of creation.

f = (2,3,4,5) # A tuple of integers

Functions

#Return a + b
def Sum(a, b):
     s = a + b
     return s# Now use it

a = Sum(2, 5)# a = 7

Files

f = open("foo","w") # Open a file for writing

g = open("bar","r") # Open a file for reading

"r" Open for reading

"w" Open for writing (truncating to zero length)

"a" Open for append

"r+" Open for read/write (updates)

"w+" Open for read/write (with truncation to zero length)

 

Examples of string processing functions

string.atof(s) # Convert to float
string.atoi(s) # Convert to integer
string.atol(s) # Convert to long
string.count(s,pattern) # Count occurrences of pattern in s.