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Python Arithmetic Operators
| Operator | Description | Example |
|---|---|---|
| + Addition | Adds values on either side of the operator. | 10 + 20 = 30 |
| - Subtraction | Subtracts right hand operand from left hand operand. | 10 – 20 = -10 |
| * Multiplication | Multiplies values on either side of the operator | 10 * 20 = 200 |
| / Division | Divides left hand operand by right hand operand | 20 / 10 = 2 |
| % Modulus | Divides left hand operand by right hand operand and returns remainder | 20 % 10 = 0 |
| ** Exponent | Performs exponential (power) calculation on operators | 10**20 =10 to the power 20 |
| // | Floor Division - The division of operands where the result is the quotient in which the digits after the decimal point are removed. But if one of the operands is negative, the result is floored, i.e., rounded away from zero (towards negative infinity) − | 9//2 = 4 and 9.0//2.0 = 4.0 -11//3 = -4 -11.0//3 = -4.0 |
Python Comparison Operators
| Info |
|---|
Below example is based on the condition as a=10, b=20 |
| Operator | Description | Example |
|---|---|---|
| == | If the values of two operands are equal, then the condition becomes true. | (a == b) is not true. |
| != | If values of two operands are not equal, then condition becomes true. | (a != b) is true. |
| <> | If values of two operands are not equal, then condition becomes true. | (a <> b) is true. This is similar to != operator. |
| > | If the value of left operand is greater than the value of right operand, then condition becomes true. | (a > b) is not true. |
| < | If the value of left operand is less than the value of right operand, then condition becomes true. | (a < b) is true. |
| >= | If the value of left operand is greater than or equal to the value of right operand, then condition becomes true. | (a >= b) is not true. |
| <= | If the value of left operand is less than or equal to the value of right operand, then condition becomes true. | (a <= b) is true. |
Data Structures - List / Set / Tuple / Dictionary
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| Code Block |
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# Import pandas as pd
import pandas as pd
# Import the cars.csv data: cars
cars = pd.read_csv('cars.csv')
# Print out cars
print(cars) |
CSV
Reading a CSV file by Pandas DataFrame with 1st column as index
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# Import pandas and cars.csv
import pandas as pd
cars = pd.read_csv('cars.csv', index_col = 0)
# Print out country column as Pandas Series
print(cars['cars_per_cap'])
# Print out country column as Pandas DataFrame
print(cars[['cars_per_cap']])
# Print out DataFrame with country and drives_right columns
print(cars[['cars_per_cap', 'country']]) |
Save a Pandas DaraFrame by CSV format
| Code Block |
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dict = {"country": ["Brazil", "Russia", "India", "China", "South Africa"],
"capital": ["Brasilia", "Moscow", "New Dehli", "Beijing", "Pretoria"],
"area": [8.516, 17.10, 3.286, 9.597, 1.221],
"population": [200.4, 143.5, 1252, 1357, 52.98] }
import pandas as pd
brics = pd.DataFrame(dict)
brics.to_csv('example.csv') |
Save a Pandas DaraFrame by CSV format with header and no index
| Code Block |
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from pandas import DataFrame
Cars = {'Brand': ['Honda Civic','Toyota Corolla','Ford Focus','Audi A4'],
'Price': [22000,25000,27000,35000]
}
df = DataFrame(Cars, columns= ['Brand', 'Price'])
export_csv = df.to_csv (r'C:\Users\Ron\Desktop\export_dataframe.csv', index = None, header=True) #Don't forget to add '.csv' at the end of the path
print (df) |
Print partial rows (observations) from a Pandas DataFrame
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# Import cars data
import pandas as pd
cars = pd.read_csv('cars.csv', index_col = 0)
# Print out first 4 observations
print(cars[0:4])
# Print out fifth, sixth, and seventh observation
print(cars[4:6]) |
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# Import cars data
import pandas as pd
cars = pd.read_csv('cars.csv', index_col = 0)
# Print out observation for Japan
print(cars.iloc[2])
# Print out observations for Australia and Egypt
print(cars.loc[['AUS', 'EG']]) |
Sort
Sort a Pandas DataFrame in an ascending order
| Info |
|---|
df.sort_values(by=['Brand'], inplace=True) |
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| Code Block |
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# sort - ascending order
from pandas import DataFrame
Cars = {'Brand': ['Honda Civic','Toyota Corolla','Ford Focus','Audi A4'],
'Price': [22000,25000,27000,35000],
'Year': [2015,2013,2018,2018]
}
df = DataFrame(Cars, columns= ['Brand', 'Price','Year'])
# sort Brand - ascending order
df.sort_values(by=['Brand'], inplace=True)
print (df) |
Sort a Pandas DataFrame in a descending order
| Info |
|---|
df.sort_values(by=['Brand'], inplace=True, ascending=False) |
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| Code Block |
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# sort - descending order
from pandas import DataFrame
Cars = {'Brand': ['Honda Civic','Toyota Corolla','Ford Focus','Audi A4'],
'Price': [22000,25000,27000,35000],
'Year': [2015,2013,2018,2018]
}
df = DataFrame(Cars, columns= ['Brand', 'Price','Year'])
# sort Brand - descending order
df.sort_values(by=['Brand'], inplace=True, ascending=False)
print (df) |
Sort a Pandas DataFrame by multiple columns
| Info |
|---|
df.sort_values(by=['First Column','Second Column',...], inplace=True) |
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