## Thursday, August 23, 2018

### (Python) Loops for Data Projects

This article was created for the purpose of demonstrating and reviewing the application of loops within the Python platform. As the title indicates, the demonstrations included within this entry will only be applicable to a limited number of scenarios. Python possesses a richness of options as it pertains to the capabilities inherent within the basic platform. I would heavily recommend further researching the topic of loops as they exist within the Python library if any of this information seems particularly difficult.

The While Loop

The “While Loop” is a simple enough concept. While a certain condition is true, a task will be implemented until the condition becomes false.

For example:

# Create counter variable #

i = 0

# Create while loop #

while i != 5:

print('Loop:', i)

i = i+1

Which produces the output:

Loop: 0
Loop: 1
Loop: 2
Loop: 3
Loop: 4

The most difficult aspect of Python “while loops” is adjusting to the Python coding syntax. For more information on the topic of loops, I would suggest performing additional research related to such.

The For Loop

The “For Loop” is similar to the “while loop” as it evaluates a condition prior to execution. However, the “for loop”, due the way in which its syntax is structured, allows for a greater customization of options which are particularly useful as it pertains to data science projects.

Let’s explore some examples which demonstrate the applicability of the “for loop”.

Using the For Loop to Cycle through a List

# Create List Variable #

list = [0, 1, 2, 3, 4, 5]

# Code the For Loop #

for x in list:

print(x)

Console Output:

0
1
2
3
4
5

Using the For Loop to Cycle through an Index

# Create List Variable #

list = [0, 1, 2, 3, 4, 5]

# Code the For Loop #

for index, list in enumerate(list):

print('Index: ', index)

print('Value: ', list)

Console Output:

Index: 0
Value: 0
Index: 1
Value: 1
Index: 2
Value: 2
Index: 3
Value: 3
Index: 4
Value: 4
Index: 5
Value: 5

Using the For Loop to Cycle through a Two Dimensional List

# Create List Variable #

list = [["Key0", 0],

["Key1", 1],

["Key2", 2],

["Key3", 3],

["Key4", 4]]

# Code the For Loop #

for x in list :

print(x[0], ":", x[1])

Console Output:

Key0 : 0
Key1 : 1
Key2 : 2
Key3 : 3
Key4 : 4

Using the For Loop to Cycle through a Dictionary

# Create Dictionary #

dictionary = {"Def0":"0", "Def1":"1", "Def2":"2", "Def3":"3", "Def4":"4"}

# Cycle through Dictionary #

for key, entry in dictionary.items():

print("Value - " + key + " : " + entry)

Console Output:

Value - Def0 : 0
Value - Def1 : 1
Value - Def2 : 2
Value - Def3 : 3
Value - Def4 : 4

Using the For Loop to Cycle through a Numpy Array

# Create List #

list = [0, 1, 2, 3, 4, 5]

# Transform list into numpy array #

numpylist = numpy.array(list)

# Cycle through list #

for x in numpylist:

print(x)

Console Output:

0
1
2
3
4

Each example independently possesses little significance. However, as we progress throughout the study of Python and continue to demonstrate example functionality, the overall usefulness of these code samples will become increasingly evident.