Python:Accumulate over a File

Accumulator Tutorials

Adding and Counting

Two Accumulators

Checking an Array

Building Strings

Using a file

Multiple Variables

Searching for Values

Harder Examples

Reprise

You may find the page on accumulating variables useful:

• Using an accumulator

How many countries in Asia?

In this example we use an accumulator to count the countries in Africa.

Notice that acc shows up three times:

• The accumulator acc is set to zero at the start.
• Every time we encounter Africa we increment acc.
• After the loop has completed acc contains the value we want - so we print it.

Change the program so that it counts the countries of Asia.

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if region == "Africa": acc = acc+1 print acc

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How many big countries?

Count the number of countries with an area of more than 1500000.

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if region == "Africa": acc = acc+1 print acc

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Numbering countries.

Produce a numbered list of countries:

  1 Afghanistan
  2 Albania
  3 Algeria
...
262 Zimbabwe

Use three character spaces for the number and put a single space after it.

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if area>1500000: acc = acc+1 print acc

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Country number 42.

Print the name of country number 42

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if area>1500000: acc = acc+1 print acc

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Total area

Calculate the total area of the world.

This time we add to the accumulator each time. We can use either of the statements below:

acc = acc + area;

acc += area;

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if area>1500000: acc = acc+1 print acc

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Total population

Calculate the total population of the world.

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if area>1500000: acc = acc+1 print acc

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Total GDP of Africa

Calculate the total GDP of the countries of Africa.

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if area>1500000: acc = acc+1 print acc

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Total GDP of the 'West'.

Calculate the total GDP of the western world. Include the regions "North America", "Europe" and "Oceania" as the western world.

.

fh = open("cia.txt","r"); acc = 0; for line in fh: f = line.split("\t") name = f[0] region = f[1] area = int(f[2]) pop = int(f[3]); gdp = int(f[4]); if area>1500000: acc = acc+1 print acc

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test text

 

 

 

 

Accumulator Tutorials

Adding and Counting

Two Accumulators

Checking an Array

Building Strings

Using a file

Multiple Variables

Searching for Values

Harder Examples

Reprise