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- left(source_string, length)
- DESCRIPTION:
Function truncates input string to a specified number of characters desired from
the left side of the string.
PARAMETERS:
source_string:
Required Argument.
Specifies a ColumnExpression of a string column or a string literal to
truncate.
Format of a ColumnExpression of a string column: '<dataframe>.<dataframe_column>.expression'.
Supported column types: CHAR, VARCHAR, and CLOB
length:
Required Argument.
Specifies a positive integer specifying the number of characters desired from
the left side of the string. If the number of character exceeds the number of
characters in the original string, the original string is returned.
Format of a ColumnExpression of a string column: '<dataframe>.<dataframe_column>.expression'.
NOTE:
Function accepts positional arguments only.
ALTERNATE NAME:
td_left
EXAMPLES:
# Load the data to run the example.
>>> load_example_data("dataframe", "admissions_train")
>>>
# Create a DataFrame on 'admissions_train' table.
>>> admissions_train = DataFrame("admissions_train")
>>> admissions_train
masters gpa stats programming admitted
id
22 yes 3.46 Novice Beginner 0
36 no 3.00 Advanced Novice 0
15 yes 4.00 Advanced Advanced 1
38 yes 2.65 Advanced Beginner 1
5 no 3.44 Novice Novice 0
17 no 3.83 Advanced Advanced 1
34 yes 3.85 Advanced Beginner 0
13 no 4.00 Advanced Novice 1
26 yes 3.57 Advanced Advanced 1
19 yes 1.98 Advanced Advanced 0
>>>
# Example truncates values in "programming" column to a length of 3.
# Import func from sqlalchemy to execute left function.
>>> from sqlalchemy import func
# Create a sqlalchemy Function object.
>>> left_func_ = func.left(admissions_train.programming.expression, 3)
>>>
# Pass the Function object as input to DataFrame.assign().
>>> df = admissions_train.assign(left_3_programming_=left_func_)
>>> print(df)
masters gpa stats programming admitted left_3_programming_
id
15 yes 4.00 Advanced Advanced 1 Adv
34 yes 3.85 Advanced Beginner 0 Beg
13 no 4.00 Advanced Novice 1 Nov
38 yes 2.65 Advanced Beginner 1 Beg
5 no 3.44 Novice Novice 0 Nov
40 yes 3.95 Novice Beginner 0 Beg
7 yes 2.33 Novice Novice 1 Nov
22 yes 3.46 Novice Beginner 0 Beg
26 yes 3.57 Advanced Advanced 1 Adv
17 no 3.83 Advanced Advanced 1 Adv
>>>
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